* Rename them to be OpenTK.NMatrix# (instead of Simd.MatrixFloat#x#).
* Remove the Vector2 and Vector4 variants, we'll use the OpenTK types instead (but we'll keep the NVector3 variant, since it's not identical to the OpenTK version).
* Update the API to match their OpenTK counterparts better:
* NMatrix2 and NMatrix3 have a 0-based R#C# scheme for their fields.
* NMatrix4 has a 1-based M## scheme for its fields (i.e. no change).
* Implement Simd vector types (VectorFloat2/3/4/VectorInt4).
* [ARKit/Vision] Use the new simd vector types instead of the OpenTK versions.
* [ModelIO] Use the new simd vectors in new API (MDLVoxelIndexExtent2).
This way we won't have to create a MDLVoxelIndexExtent3 in the future.
* [SpriteKit] Use the new simd vectors in new API.
ARPointCloud.RawFeaturePoints is an array of Vector3, but each vector is
16-byte aligned (as if it were an array of Vector4).
This means we need to account for this when creating a managed array from
pointer to the native C-style array.
Rolf Bjarne Kvinge
Vincent Dondain