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`.
Changing the Input Map in Project Settings (adding/removing/renaming actions, reordering, or changing action events) causes the action list Tree to be cleared/repopulated. Updated ActionMapEditor::update_action_list to store which actions were collapsed before clearing, so they can remain collapsed after modifications.
