Modify `UVStretchAngle` vertex struct alignment to match
4-byte struct alignment for Metal. This includes reordering
array elements to the front and adding additional padding
to the struct in Metal such that the raw-data write size
matches the padded vertex format.
Authored by Apple: Michael Parkin-White
Pull Request: https://projects.blender.org/blender/blender/pulls/114923
b8c84d03cd