Preserve more MD_mem_parallel_loop_access and MD_access_group in SROA

SROA sometimes preserves MD_mem_parallel_loop_access and MD_access_group metadata on loads/stores, and sometimes fails to do so. This change adds copying of the MD after other CreateAlignedLoad/CreateAlignedStores. Also fix a case where the metadata was being copied from a load, rather than the store.

Added a LIT test to catch one case.

Patch by Mark Mendell

Differential Revision: https://reviews.llvm.org/D103254