Split omp_partial_update test to test individual features.

[jefflarkin]

The partial_update OpenMP test currently tests more than just partial update, leading to a false fail when partial updating works, but either map(always:) or nowait causes a failure. This introduces more tests to validate each of those parts individually.

• partial_update test renamed to partial_update_full to preserve the existing test
• A new partial_update test is added that uses a target update in place of always and does not use nowait
• A new map_always test is created it test support of the always modifier
• A new nowait_taskwait test is created, which mimics the original test, but does not rely on the always modifier

This should allow for better test coverage of specific OpenMP offloading features.

[qmc-robot]

Can one of the admins verify this patch?

[ye-luo]

LGTM. Thanks.