[llvm] [LLVM-C] Upstream `LLVMBuild{Min, Max}Num` from rustc (PR #162500)

[via llvm-commits]

AMS21 wrote:

> I'm not sure why we have these functions on the Rust side at all. minnum and maxnum are just normal intrinsics, so we should just do something like `self.call_intrinsic("llvm.minnum", &[self.val_ty(lhs)], &[lhs, rhs])`.
> This also applies to all the LLVMRustBuildVectorReduceXYZ functions.

Good question. Seems like they were added 8 Years ago with https://github.com/rust-lang/rust/commit/7d5343a6700581e318189dcd74567b348bd7f68d and https://github.com/rust-lang/rust/commit/01cc5b3e195bb01088fdd59638f0d8c6d0a78142.
I'll close this and refactor this on the rust side instead :)

https://github.com/llvm/llvm-project/pull/162500