[llvm] [SCEV] Retain SCEVSequentialMinMaxExpr if an operand may trigger UB. (PR #92177)

[Florian Hahn via llvm-commits]

fhahn wrote:

@nikic WDYT about the added comment?

I also added SCEV-only tests, so the SCEV changes could be separated from the SCEVExpander changes if preferred

https://github.com/llvm/llvm-project/pull/92177