This allows removing it from `class_db.h`, significantly reducing the amount of files
that include it transitively.
Also includes some include cleanup in `control.h` and `rich_text_label.h` done while
ensure they don't depend on `callable_mp`.
This time as an EditorPlugin!
Improve rendering of inner area of MarginContainer
Decrease thickness and opacity of lines, and render margins as a rectangle rather than lines extending to the edges of the bounding box
Apply suggestions from code review
Co-authored-by: Tomasz Chabora <kobewi4e@gmail.com>
Use `get_margin_size`, change color of viz border, and trigger redraw on MarginContainer's draw signal
Rémi Verschelde