[llvm] [ValueTracking] Extend LHS/RHS with matching operand to work without constants. (PR #85557)

[via llvm-commits]

goldsteinn wrote:

@nikic, is the idea of this patch okay? Or are you strongly opposed to using `computeConstantRange` here.
Ill rework if thats the case (want to at least handle basic stuff like `X u> Y -> X != 0` which we don't need `computeConstantRange` for).

https://github.com/llvm/llvm-project/pull/85557