[llvm] [GIsel] import min/max rewrites (PR #188267)

[Luisa Cicolini via llvm-commits]

luisacicolini wrote:

thanks @arsenm @davemgreen for the comments! I've addressed everything. @davemgreen I can work on adding abs in another PR if that's useful?

https://github.com/llvm/llvm-project/pull/188267