Generically implement fn horizontal_{min,max}

[workingjubilee]

This collapses all instances of these two functions by merely depending on T being SimdElement + PartialOrd.

[workingjubilee]

This only saves 18kb, but it makes the docs much easier to navigate, so.

[programmerjake]

lgtm

[calebzulawski]

I mentioned this in zulip, I don't think PartialOrd is the correct bound, we probably want our own trait that specifically means that these functions monomorphize.

[calebzulawski]

A trivial example--pointers implement PartialOrd but do we want them to implement these functions? We might, might not, and I have no idea if these functions would monomorphize.

[workingjubilee]

That is not an actual concern in any of our exposed interfaces and was not a blocking concern for introducing the prior versions.

[workingjubilee]

Consensus coalesced around a different direction than here.