[llvm] [Codegen, X86] Add prefetch insertion based on Propeller profile (PR #166324)

[Aiden Grossman via llvm-commits]

https://github.com/boomanaiden154 approved this pull request.

LGTM.

It would be nice to add a NewPM port of `InsertCodePrefetch`, but given that pass already exists, we can just do that in a future PR when it comes up.

https://github.com/llvm/llvm-project/pull/166324