[Transforms] Propagate new-format TBAA tags on simplification of memory-transfer intrinsics

With this patch in place, when a new-format TBAA tag is available
for a memory-transfer intrinsic call, we prefer propagating that
new-format tag. Otherwise, we fallback to the old approach where
we try to construct a proper TBAA access tag from 'tbaa.struct'
metadata.

Differential Revision: https://reviews.llvm.org/D41543

llvm-svn: 325488