WIP port to wide from std-simd

[Elabajaba]

I was bored and wanted to see what this would look like on stable rust using wide instead of portable-simd since that requires nightly and doesn't seem like it's getting stabilized anytime soon.

I don't have anything using this crate currently, so don't consider this a feature request. If you're interested in having this run on stable rust I can finish it (I'm also considering trying pulp since it seems to be a closer match to portable-simd, but that also seems to lack a simd_swizzle! equivalent).

There's still a couple hundred errors needed to fix in math.rs (mostly just a ton of simd_swizzle! that look annoying to fix, and a few errors in other files).