pragma_unroll tests not testing a pragma

The tests in `test_conformance/compiler/test_pragma_unroll.cpp` are not testing a pragma but a function attribute. Why have they been named that way? Should they be renamed for clarity?

Start by reading test_conformance/compiler/test_pragma_unroll.cpp and compare the tests' function-attribute coverage with the filename and test names. Rename the file and related tests so they accurately describe what they test, then verify the compiler conformance tests still discover and run them.

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