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

[Florian Hahn via llvm-commits]

fhahn wrote:

Example uses:

* Use SCEVUse to add additional NUW flag when reasoning in LAA: https://github.com/llvm/llvm-project/pull/91962
* get SCEV for Value with use-specific flags (only implemented for GEP exprs for now): https://github.com/llvm/llvm-project/pull/91964

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