[llvm] Intrinsic: introduce minimumnum and maximumnum for IR and SelectionDAG (PR #96649)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> > Given the size and churn on this patch, I have a slight preference to split it into two patches : IR and backend.
> 
> I guess that it need a minimum use case to compose a full patch.

It's perfectly fine to only define the intrinsic in one patch, and implement codegen in another

https://github.com/llvm/llvm-project/pull/96649