[InlineFunction] Update metadata on loads that are return values

This patch builds upon D76140 by updating metadata on pointer typed
loads in inlined functions, when the load is the return value, and the
callsite contains return attributes which can be updated as metadata on
the load.
Added test cases show this for nonnull, dereferenceable,
dereferenceable_or_null

Reviewed-By: jdoerfert

Differential Revision: https://reviews.llvm.org/D76792