Replace Matrix.Equals() with simd implementation (OTK4)

[BoyBaykiller]

This PR ports #1721 to OpenTK4.
Interestingly I needed to add [MethodImpl(MethodImplOptions.AggressiveInlining)] for there to be any significant performance improvement.

[BoyBaykiller]

I've personally switched to OTK5 and don't need this anymore. The SIMD implementation in OTK5 is also much cleaner.
I would be fine with closing this PR if you don't think it's worth it in general.

[NogginBops]

Sorry for not getting to these PRs faster.
As you say, the implementation here is quite messy compared to the OTK5 one, so it's probably easiest to just get that PR in and close this one.
Unless we have more people interested in faster matrix equality checks for OTK4.