[SYCL] Implement work group memory extension

[lbushi25]

Implement work group memory extension: https://github.com/intel/llvm/blob/sycl/sycl/doc/extensions/proposed/sycl_ext_oneapi_work_group_memory.asciidoc
Two notes:

• Free function kernel support for work group memory argument will be added in a future PR.
• When the assignment operator is called in host code, the assigned to work group memory object does not actually correspond to the same underlying memory as the one that was assigned from contradicting the spec. See Does "local_accessor" really have common reference semantics? KhronosGroup/SYCL-Docs#552 for a similar problem with local_accessor

[lbushi25]

@intel/dpcpp-cfe-reviewers ping for review of the frontend changes and tests.

[elizabethandrews]

Please add FE tests for FE changes. Since you're adding a new type of argument with some special handling in the FE, I would add an AST test ensuring the expected arguments are generated and a CodeGen test for the change in integration header.

[elizabethandrews]

Please add FE tests for FE changes. Since you're adding a new type of argument with some special handling in the FE, I would add an AST test ensuring the expected arguments are generated and a CodeGen test for the change in integration header.

Please add FE tests for FE changes. Since you're adding a new type of argument with some special handling in the FE, I would add an AST test ensuring the expected arguments are generated and a CodeGen test for the change in integration header.

My bad. I did not notice the test you added. No further changes are necessary

[lbushi25]

@intel/llvm-gatekeepers ping for merge.