[llvm] [BOLT] Introduce helpers to match `MCInst`s one at a time (NFC) (PR #138883)

[Maksim Panchenko via llvm-commits]

https://github.com/maksfb commented:

Neat.

I'm in favor of renaming one of `MCInstMatcher` classes instead of just keeping them in different namespaces. If the functionality can be merged, it sounds good to me as well.

https://github.com/llvm/llvm-project/pull/138883