[llvm] [SCEV] Support ule/sle exit counts via widening (PR #92206)

[Florian Hahn via llvm-commits]

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

LGTM, thanks!

IIUC the more expensive expansions should be taken care of mostly by `isHighCostExpansion` for cases where we now compute more complicated BTCs (vs not being able to compute them before).

Would still be good to wait a day or so in case @efriedma-quic has additional thoughts

https://github.com/llvm/llvm-project/pull/92206