`NOTIFICATION_MOUSE_ENTER` and `NOTIFICATION_MOUSE_EXIT` now includes
the areas of children control nodes if the mouse filters allow it.
In order to check if a Control node itself was entered/exited, the newly
introduced `NOTIFICATION_MOUSE_ENTER_SELF` and
`NOTIFICATION_MOUSE_EXIT_SELF` can be used.
Co-authored-by: Markus Sauermann <6299227+Sauermann@users.noreply.github.com>