[llvm] [InstCombine] Reassociate commutative binops over select/phi/minmax (PR #187493)

[Mitch Briles via llvm-commits]

MitchBriles wrote:

@dtcxzyw I'm still not sure whether to use `OuterOp.dropUnknownNonDebugMetadata();`, `dropUBImplyingAttrsAndMetadata`, or `dropUBImplyingAttrsAndUnknownMetadata`. Also had to change tests after rebase due to a change to `!noundef`.

https://github.com/llvm/llvm-project/pull/187493