Add fix for propagation of !pcsections metadata for expanded atomics,
together with more tests for interesting atomic instructions (based on
llvm/test/CodeGen/AArch64/GlobalISel/arm64-atomic.ll).
Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D133710
Interpret MD_pcsections in AsmPrinter emitting the requested metadata to
the associated sections. Functions and normal instructions are handled.
Differential Revision: https://reviews.llvm.org/D130879