[llvm] [Transforms] Recognize memcmp-like loops in LoopIdiomRecognize (PR #181562)

[Sayan Sivakumaran via llvm-commits]

sivakusayan wrote:

This is my first somewhat larger PR here that isn't a "good-first-issue", so apologies if there are some basic mistakes. I tried to use [this similar PR](https://github.com/llvm/llvm-project/pull/108985) to help guide my implementation.

https://github.com/llvm/llvm-project/pull/181562