This add back the NDC offset that was present in the legacy overlay.
But instead of adding a new view for it, we add `ndc_offset_factor`
to `State` to simplify wire offseting
Instead of modifying the projection matrix, we compute the unit
offset and pass it to the shader which choose the appropriate
factor to apply to the vertex position.
The value is put inside `State` so that it can be referenced
easily by multiple overlays.
Later on (once we move the global UBO inside Overlay) we can
move this to a UBO.
This only implements it for wireframe and edit mesh vert and
edges.
Note: that there seems to be some code duplication with the
edit mesh vertex code. That's to be tackled in another commit.
Pull Request: https://projects.blender.org/blender/blender/pulls/133433
cfd5d9e3ad