[llvm] [InstCombine] Fold `(select C, (x bin_op a), x) bin_op b` into `x bin_op select C, (a bin_op b), b` (PR #173511)

[Gábor Spaits via llvm-commits]

spaits wrote:

@dtcxzyw thank you for reviewing my PR. I think I have addressed the comments and also squashed the commits.

https://github.com/llvm/llvm-project/pull/173511