[Transforms] Propagate TBAA info in SROA

Now that we have the new TBAA metadata format that is capable of
representing accesses to aggregates, we can propagate TBAA access
tags from memory setting and transferring intrinsics to load and
store instructions and vice versa.

Since SROA produces lots of new loads and stores on optimized
builds, this change significantly decreases the share of
undecorated memory accesses on such builds.

Differential Revision: https://reviews.llvm.org/D41563

llvm-svn: 325329