In Vulkan the grid overlay wasn't rendering correctly. The reason was
a mis alignment in the std430 layout. This PR fixes the std430 layout
so the grid overlay (and perhaps also other sections) would work.
Root cause is that the reserve size if an nVec3 is different when used
as an array versus a single attribute. This was not taken into account
where the overlay flag was read from uninitialized memory.
Pull Request: https://projects.blender.org/blender/blender/pulls/112564
2d70f46265