When `COMP_U*` is used together with a `GPU_FETCH_INT` the backend
tried to convert them to floats. What is of course not what should
happen.
Issue was that these cases were never correctly tested. With this
change the `data` attribute of the `overlay_edit_mesh` shaders are
transferred correctly and can draw some pixels as intended.
Pull Request: https://projects.blender.org/blender/blender/pulls/112270