Add "Distraction Free Mode" button to EditorBottomPanel when bottom panel is expanded

[arkology]

Attempt to resolve godotengine/godot-proposals#12052

godot.windows.editor.dev.x86_64_MGoiltojRG.mp4

[KoBeWi]

The button has wrong pressed style:

Also reparenting feels a bit hacky. I think it would be fine if the button was duplicated, then you could just toggle visibility. Only the visible button can process shortcut, so it should work properly.
EDIT:
I guess syncing the state of buttons would become a problem.

[arkology]

@KoBeWi button theme should be fixed now.
As I mentioned in feature proposal, I'm not a big fan of my implementation, but it is functional and not very overengineered (IMO).
Any suggestions are welcomed. If I understood your comment correctly, creating a duplicate of this button and trying to synchronize its state is also a hacky solution, and it also makes no sense to consider this option, right?

[KoBeWi]

This solution is ok.

We don't have any simple way to sync pressed state of 2 buttons (there is ButtonGroup, but for basically an opposite use-case), so any solution would likely involve hacks.