[MTE] Handle MTE instructions in AArch64LoadStoreOptimizer.

Summary: Generate pre- and post-indexed forms of ST*G and STGP when possible.

Reviewers: ostannard, vitalybuka

Subscribers: kristof.beyls, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67741

llvm-svn: 372412