Add sanitizer metadata attributes to clang IR gen.

This patch adds generation of sanitizer metadata attributes (which were
added in D126100) to the clang frontend.

We still currently generate the `llvm.asan.globals` that's consumed by
the IR pass, but the plan is to eventually migrate off of that onto
purely debuginfo and these IR attributes.

Reviewed By: vitalybuka, kstoimenov

Differential Revision: https://reviews.llvm.org/D126929