[llvm] [InstCombine] Improve coverage of `foldSelectValueEquivalence` for non-constants (PR #94719)

[via llvm-commits]

goldsteinn wrote:

Dropped the use-reduction code. Think for this to inf loop you would need to violate SSA i.e: f(x, y) -> y -> y(x, z) -> x. For us to go from x -> y, then y would need to both be dominated by x and dominate x.

https://github.com/llvm/llvm-project/pull/94719