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

[Nikita Popov via llvm-commits]

nikic wrote:

> > Before landing, just to recap on the compile-time impact of the change and follow-up changes needed
> 
> I assume we are fine with the impact and the general future direction/follow-up changes and will go ahead and merge this in a bit, unless I hear otherwise :)

Yes, I'm fine with the impact.

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