Add overlay option to disable grid drawing.
Reuse drawing code from other editors (timeline editor)
Add argument `display_minor_lines` to function
`UI_view2d_draw_lines_x__discrete_frames_or_seconds`
This way minor line drawing can be disabled and so it doesn't cause
too much visual noise. Also spacing seems to be too fine, so VSE uses 3x
what is defined in preferences.
Reviewed By: fsiddi, Severin
Differential Revision: https://developer.blender.org/D11790
0491052a96
