[llvm] [BOLT][Passes] use DenseMap/SmallPtrSet in CacheMetrics and TailDupli… (PR #205480)

[Paschalis Mpeis via llvm-commits]

https://github.com/paschalis-mpeis approved this pull request.

Hey @devnexen,

Looks good overall. Could you mark the title as `[NFC]`?

Out of curiosity, did you observe any before/after impact that motivated this change, or was this a general ADT cleanup?

https://github.com/llvm/llvm-project/pull/205480