Basic MTE stack tagging instrumentation.

Summary:
Use MTE intrinsics to tag stack variables in functions with
sanitize_memtag attribute.

Reviewers: pcc, vitalybuka, hctim, ostannard

Subscribers: srhines, mgorny, javed.absar, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64173

llvm-svn: 366361