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

[Anatoly Trosinenko via llvm-commits]

atrosinenko wrote:

Rebased the stack after #155846 was merged. I plan waiting a bit more to make sure I don't have to rollback the patch again and then merging this PR, then I will check if it is possible to reorder the remaining patches, to land already approved PRs #139778 and #141665.

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