Create CMake function to clean up declaring regular/full libraries for mixed builds

[sharon-wang]

Proposed in #11662 (comment).

For several libraries (those split into regular/compressed and full for mixed references builds), there exists a pattern to declare one (regular lib) or two versions (regular/compressed and full) of the library depending on OMR_MIXED_REFERENCES_MODE_STATIC.

Since this pattern exists in many CMake files, it would be cleaner to write a function to encapsulate the splitting.

More mixed builds discussion: #8878.