[llvm] [InstCombine] Use the select condition to try to constant fold binops into select (PR #84696)

[via llvm-commits]

goldsteinn wrote:

> > 
> > I still don't like these things happen :( It is okay for div/rem. But I am not sure it is always a win for mul. We need to discuss this problem with other backend maintainers.
> 
> I'm happy to drop this for `mul` and only keep for `div`/`rem`.

Dropped folding of multi-use `select` w/ `mul` + tests.

https://github.com/llvm/llvm-project/pull/84696