Improve descriptions of the process executions for PEX_PATH composition.

[stuhood]

Followup to #12675 to improve the process descriptions surrounding PEX_PATH composition.

This only meaningfully affects the output when lockfiles / constraints-file are in use. Afterwards, the output in that case looks like:

$ ./pants --no-process-execution-local-cache --no-remote-cache-read test src/python/pants/util/::
16:20:12.69 [INFO] Completed: Building requirements.pex
16:20:33.47 [INFO] Completed: Resolving pytest.pex from 3rdparty/python/lockfiles/pytest.txt
16:20:36.88 [INFO] Completed: Resolving 3rdparty/python/lockfiles/user_reqs.txt
16:20:38.05 [INFO] Completed: Building pytest_runner.pex
16:20:41.32 [INFO] Completed: test - src/python/pants/util/osutil_test.py:tests succeeded.
16:20:41.96 [INFO] Completed: test - src/python/pants/util/filtering_test.py:tests succeeded.
16:20:41.96 [INFO] Completed: test - src/python/pants/util/eval_test.py:tests succeeded.
16:20:41.97 [INFO] Completed: test - src/python/pants/util/socket_test.py:tests succeeded.
16:20:42.70 [INFO] Completed: Extracting ansicolors==1.1.8 from lockfile.pex
16:20:42.72 [INFO] Completed: Extracting typing-extensions==3.7.4.3 from lockfile.pex
16:20:42.85 [INFO] Completed: Extracting packaging==21.0 from lockfile.pex
16:20:44.56 [INFO] Completed: test - src/python/pants/util/memo_test.py:tests succeeded.
16:20:44.65 [INFO] Completed: test - src/python/pants/util/enums_test.py:tests succeeded.
16:20:44.70 [INFO] Completed: Extracting pytest<6.3,>=6.0.1 from lockfile.pex
16:20:46.86 [INFO] Completed: Composing 2 requirements to build requirements.pex from lockfile.pex
16:20:47.04 [INFO] Completed: Composing 1 requirement to build requirements.pex from lockfile.pex
16:20:48.48 [INFO] Completed: Composing 1 requirement to build requirements.pex from lockfile.pex
16:20:53.01 [INFO] Completed: Building pytest_runner.pex
16:20:53.04 [INFO] Completed: Building pytest_runner.pex
16:20:55.50 [INFO] Completed: test - src/python/pants/util/docutil_test.py:tests succeeded.
16:20:55.73 [INFO] Completed: Building pytest_runner.pex
16:20:56.09 [INFO] Completed: test - src/python/pants/util/contextutil_test.py:tests succeeded.
16:20:56.09 [INFO] Completed: test - src/python/pants/util/dirutil_test.py:tests succeeded.
16:20:58.00 [INFO] Completed: test - src/python/pants/util/collections_test.py:tests succeeded.
16:20:58.27 [INFO] Completed: test - src/python/pants/util/meta_test.py:tests succeeded.
16:20:58.45 [INFO] Completed: test - src/python/pants/util/frozendict_test.py:tests succeeded.
16:20:58.52 [INFO] Completed: test - src/python/pants/util/strutil_test.py:tests succeeded.
16:20:58.56 [INFO] Completed: test - src/python/pants/util/ordered_set_test.py:tests succeeded.

✓ src/python/pants/util/collections_test.py:tests succeeded.
✓ src/python/pants/util/contextutil_test.py:tests succeeded.
✓ src/python/pants/util/dirutil_test.py:tests succeeded.
✓ src/python/pants/util/docutil_test.py:tests succeeded.
✓ src/python/pants/util/enums_test.py:tests succeeded.
✓ src/python/pants/util/eval_test.py:tests succeeded.
✓ src/python/pants/util/filtering_test.py:tests succeeded.
✓ src/python/pants/util/frozendict_test.py:tests succeeded.
✓ src/python/pants/util/memo_test.py:tests succeeded.
✓ src/python/pants/util/meta_test.py:tests succeeded.
✓ src/python/pants/util/ordered_set_test.py:tests succeeded.
✓ src/python/pants/util/osutil_test.py:tests succeeded.
✓ src/python/pants/util/socket_test.py:tests succeeded.
✓ src/python/pants/util/strutil_test.py:tests succeeded.

[ci skip-rust]
[ci skip-build-wheels]

[Eric-Arellano]

Very nice

[stuhood]

@jsirois : I'm going to continue reviewing/running-the-numbers on pex-tool/pex#1431 tonight, but will pipeline landing this in case we continue on the current path.