[codeview] Fix for PR43479

Summary:
Add instruction marker to MachineInstr ExtraInfo. This does almost the
same thing as Pre/PostInstrSymbols, except that it doesn't create a label until
printing instructions. This allows for labels to be put around instructions that
are deleted/duplicated somewhere.
Use this marker to track heap alloc site call instructions.

Reviewers: rnk

Subscribers: MatzeB, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D69536

cherry picked from 74204304 with some
modifications.