[llvm] [polly] [SCEV] Introduce SCEVUse, use it instead of const SCEV * (NFCI) (WIP). (PR #91961)

[Florian Hahn via llvm-commits]

fhahn wrote:

Ping :) rebased after landing pattern matching and fixed the polly build failures.

Current CT impact: https://llvm-compile-time-tracker.com/compare.php?from=4e828f8d741ff61317bb1e0b67f22e274632b07a&to=f3905cdaf342e506e1e40dbef4d23b031dd83bd9&stat=instructions:u

https://github.com/llvm/llvm-project/pull/91961