Add way to omit debug-location from MIR output

Summary:
In lieu of a proper pass that strips debug info, add a way
to omit debug-locations from the MIR output so that
instructions with MMO's continue to match CHECK's when
mir-debugify is used

Reviewers: aprantl, bogner, vsk

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D77575