This commit adds exceptions to the `files_same` function in the pkg_editor unit tests.

Previously, the tests would pass even if one of the files passed into `files_same` did not exist. By adding exceptions, we correctly error out if one of the files did not exist.

This commit adds randomness to the pkg_editor unit tests that deal with packing and unpacking files. This ensures that we can cover all file sizes and all types of file contents and improves the robustness of our pkg_editor code.

The info.name_length variable was not being checked to see if it was less than the size of name when passed into read_data. This was a simple fix.

Fixes:
```
lib/pkg_editor/src/pkg_editor.c:1632:5:
  Type: Untrusted value as argument (TAINTED_SCALAR)

lib/pkg_editor/src/pkg_editor.c:1591:3: Tainted data flows to a taint sink
  1. path: Condition "buffer != NULL", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1596:5:
  2. path: Condition "input != NULL", taking true branch.
lib/pkg_editor/src/pkg_editor.c:1596:5:
  3. path: Falling through to end of if statement.
lib/pkg_editor/src/pkg_editor.c:1601:3:
  4. path: Condition "ret != 0", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1612:3:
  5. path: Condition "z_info.strm.avail_in > 0", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1612:3:
  6. path: Condition "input != NULL", taking true branch.
lib/pkg_editor/src/pkg_editor.c:1612:3:
  7. path: Condition "!feof(input)", taking true branch.
lib/pkg_editor/src/pkg_editor.c:1614:5:
  8. path: Condition "!read_data(&info, 20UL /* sizeof (info) */, &z_info, input)", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1619:5:
  9. path: Condition "info.magic != 3203399403U", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1627:5:
  10. path: Condition "info.kind == PACK_END", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1632:5:
  11. path: Condition "!read_data(name, info.name_length, &z_info, input)", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1642:5:
  12. path: Condition "out_dir_length + 2 > 12288UL /* 3 * 4096 */", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1652:5:
  13. path: Condition "info.kind == PACK_DIR", taking true branch.
lib/pkg_editor/src/pkg_editor.c:1654:5:
  14. path: Falling through to end of if statement.
lib/pkg_editor/src/pkg_editor.c:1711:3:
  15. path: Jumping back to the beginning of the loop.
lib/pkg_editor/src/pkg_editor.c:1612:3:
  16. path: Condition "z_info.strm.avail_in > 0", taking true branch.
lib/pkg_editor/src/pkg_editor.c:1614:5:
  17. path: Condition "!read_data(&info, 20UL /* sizeof (info) */, &z_info, input)", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1619:5:
  18. path: Condition "info.magic != 3203399403U", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1627:5:
  19. path: Condition "info.kind == PACK_END", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1632:5:
  20. path: Condition "!read_data(name, info.name_length, &z_info, input)", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1642:5:
  21. path: Condition "out_dir_length + 2 > 12288UL /* 3 * 4096 */", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1652:5:
  22. path: Condition "info.kind == PACK_DIR", taking true branch.
lib/pkg_editor/src/pkg_editor.c:1654:5:
  23. path: Falling through to end of if statement.
lib/pkg_editor/src/pkg_editor.c:1711:3:
  24. path: Jumping back to the beginning of the loop.
lib/pkg_editor/src/pkg_editor.c:1612:3:
  25. path: Condition "z_info.strm.avail_in > 0", taking true branch.
lib/pkg_editor/src/pkg_editor.c:1614:5:
  26. tainted_argument: Calling function "read_data" taints argument "info".
lib/pkg_editor/src/pkg_editor.c:1530:3: Tainted data flows to a taint sink
  26.1. var_assign_parm: Assigning: "z_info->strm.next_out" = "data".
lib/pkg_editor/src/pkg_editor.c:1534:5:
  26.2. path: Condition "z_info->strm.avail_in == 0", taking true branch.
lib/pkg_editor/src/pkg_editor.c:1537:7:
  26.3. path: Condition "in_fd == NULL", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1537:7:
  26.4. path: Condition "feof(in_fd)", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1541:7:
  26.5. tainted_data_argument: Calling function "fread" taints parameter "*z_info->buffer". [Note: The source code implementation of the function has been overridden by a builtin model.]
lib/pkg_editor/src/pkg_editor.c:1542:7:
  26.6. path: Condition "count < 1", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1547:7:
  26.7. var_assign_alias: Assigning: "z_info->strm.next_in" = "z_info->buffer", which taints "z_info->strm.next_in".
lib/pkg_editor/src/pkg_editor.c:1550:5:
  26.8. tainted_data_transitive: Calling function "inflate" with tainted argument "*z_info->strm.next_in" taints "*z_info->strm.next_out".
lib/pkg_editor/src/pkg_editor.c:1551:5:
  26.9. path: Condition "ret != -2", taking true branch.
lib/pkg_editor/src/pkg_editor.c:1551:5:
  26.10. path: Falling through to end of if statement.
lib/pkg_editor/src/pkg_editor.c:1552:5:
  26.11. path: Condition "ret == 1", taking true branch.
lib/pkg_editor/src/pkg_editor.c:1554:7:
  26.12. path: Condition "z_info->strm.avail_out == 0", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1614:5:
  27. path: Condition "!read_data(&info, 20UL /* sizeof (info) */, &z_info, input)", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1619:5:
  28. path: Condition "info.magic != 3203399403U", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1627:5:
  29. path: Condition "info.kind == PACK_END", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1632:5:
  30. tainted_data: Passing tainted expression "info.name_length" to "read_data", which uses it as an offset.
lib/pkg_editor/src/pkg_editor.c:1531:3: Tainted data flows to a taint sink
  30.1. var_assign_parm: Assigning: "z_info->strm.avail_out" = "size", which taints "z_info->strm.avail_out".
lib/pkg_editor/src/pkg_editor.c:1534:5:
  30.2. path: Condition "z_info->strm.avail_in == 0", taking true branch.
lib/pkg_editor/src/pkg_editor.c:1537:7:
  30.3. path: Condition "in_fd == NULL", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1537:7:
  30.4. path: Condition "feof(in_fd)", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1542:7:
  30.5. path: Condition "count < 1", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1550:5:
  30.6. taint_sink_lv_call: Passing tainted expression "z_info->strm.avail_out" to taint sink "inflate".
lib/pkg_editor/src/pkg_editor.c:1632:5:
  31. remediation: Ensure that tainted values are properly sanitized, by checking that their values are within a permissible range.
```

Fixes:
```
lib/pkg_editor/src/pkg_editor.c:1681:11:
  Type: Untrusted allocation size (TAINTED_SCALAR)

lib/pkg_editor/src/pkg_editor.c:1591:3: Tainted data flows to a taint sink
  1. path: Condition "buffer != NULL", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1596:5:
  2. path: Condition "input != NULL", taking true branch.
lib/pkg_editor/src/pkg_editor.c:1596:5:
  3. path: Falling through to end of if statement.
lib/pkg_editor/src/pkg_editor.c:1601:3:
  4. path: Condition "ret != 0", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1612:3:
  5. path: Condition "z_info.strm.avail_in > 0", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1612:3:
  6. path: Condition "input != NULL", taking true branch.
lib/pkg_editor/src/pkg_editor.c:1612:3:
  7. path: Condition "!feof(input)", taking true branch.
lib/pkg_editor/src/pkg_editor.c:1614:5:
  8. path: Condition "!read_data(&info, 20UL /* sizeof (info) */, &z_info, input)", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1619:5:
  9. path: Condition "info.magic != 3203399403U", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1627:5:
  10. path: Condition "info.kind == PACK_END", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1632:5:
  11. path: Condition "!read_data(name, info.name_length, &z_info, input)", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1642:5:
  12. path: Condition "out_dir_length + 2 > 12288UL /* 3 * 4096 */", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1652:5:
  13. path: Condition "info.kind == PACK_DIR", taking true branch.
lib/pkg_editor/src/pkg_editor.c:1654:5:
  14. path: Falling through to end of if statement.
lib/pkg_editor/src/pkg_editor.c:1711:3:
  15. path: Jumping back to the beginning of the loop.
lib/pkg_editor/src/pkg_editor.c:1612:3:
  16. path: Condition "z_info.strm.avail_in > 0", taking true branch.
lib/pkg_editor/src/pkg_editor.c:1614:5:
  17. path: Condition "!read_data(&info, 20UL /* sizeof (info) */, &z_info, input)", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1619:5:
  18. path: Condition "info.magic != 3203399403U", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1627:5:
  19. path: Condition "info.kind == PACK_END", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1632:5:
  20. path: Condition "!read_data(name, info.name_length, &z_info, input)", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1642:5:
  21. path: Condition "out_dir_length + 2 > 12288UL /* 3 * 4096 */", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1652:5:
  22. path: Condition "info.kind == PACK_DIR", taking true branch.
lib/pkg_editor/src/pkg_editor.c:1654:5:
  23. path: Falling through to end of if statement.
lib/pkg_editor/src/pkg_editor.c:1711:3:
  24. path: Jumping back to the beginning of the loop.
lib/pkg_editor/src/pkg_editor.c:1612:3:
  25. path: Condition "z_info.strm.avail_in > 0", taking true branch.
lib/pkg_editor/src/pkg_editor.c:1614:5:
  26. tainted_argument: Calling function "read_data" taints argument "info".
lib/pkg_editor/src/pkg_editor.c:1530:3: Tainted data flows to a taint sink
  26.1. var_assign_parm: Assigning: "z_info->strm.next_out" = "data".
lib/pkg_editor/src/pkg_editor.c:1534:5:
  26.2. path: Condition "z_info->strm.avail_in == 0", taking true branch.
lib/pkg_editor/src/pkg_editor.c:1537:7:
  26.3. path: Condition "in_fd == NULL", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1537:7:
  26.4. path: Condition "feof(in_fd)", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1541:7:
  26.5. tainted_data_argument: Calling function "fread" taints parameter "*z_info->buffer". [Note: The source code implementation of the function has been overridden by a builtin model.]
lib/pkg_editor/src/pkg_editor.c:1542:7:
  26.6. path: Condition "count < 1", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1547:7:
  26.7. var_assign_alias: Assigning: "z_info->strm.next_in" = "z_info->buffer", which taints "z_info->strm.next_in".
lib/pkg_editor/src/pkg_editor.c:1550:5:
  26.8. tainted_data_transitive: Calling function "inflate" with tainted argument "*z_info->strm.next_in" taints "*z_info->strm.next_out".
lib/pkg_editor/src/pkg_editor.c:1551:5:
  26.9. path: Condition "ret != -2", taking true branch.
lib/pkg_editor/src/pkg_editor.c:1551:5:
  26.10. path: Falling through to end of if statement.
lib/pkg_editor/src/pkg_editor.c:1552:5:
  26.11. path: Condition "ret == 1", taking true branch.
lib/pkg_editor/src/pkg_editor.c:1554:7:
  26.12. path: Condition "z_info->strm.avail_out == 0", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1614:5:
  27. path: Condition "!read_data(&info, 20UL /* sizeof (info) */, &z_info, input)", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1619:5:
  28. path: Condition "info.magic != 3203399403U", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1627:5:
  29. path: Condition "info.kind == PACK_END", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1632:5:
  30. path: Condition "!read_data(name, info.name_length, &z_info, input)", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1642:5:
  31. path: Condition "out_dir_length + 2 > 12288UL /* 3 * 4096 */", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1652:5:
  32. path: Condition "info.kind == PACK_DIR", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1657:7:
  33. path: Condition "out_file == NULL", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1663:7:
  34. path: Condition "info.file_length > 0", taking true branch.
lib/pkg_editor/src/pkg_editor.c:1663:7:
  35. lower_bounds: Checking lower bounds of unsigned scalar "info.file_length" by taking the true branch of "info.file_length > 0U".
lib/pkg_editor/src/pkg_editor.c:1665:9:
  36. path: Condition "info.file_length < 65536UL /* sizeof (buf) */", taking false branch.
lib/pkg_editor/src/pkg_editor.c:1665:9:
  37. lower_bounds: Checking lower bounds of unsigned scalar "info.file_length" by taking the false branch of "info.file_length < 65536UL".
lib/pkg_editor/src/pkg_editor.c:1681:11:
  38. tainted_data: Passing tainted expression "info.file_length" to "malloc", which uses it as an allocation size.
lib/pkg_editor/src/pkg_editor.c:1681:11:
  39. remediation: Ensure that tainted values are properly sanitized, by checking that their values are within a permissible range.
```