Fix broken bottom panel switching

[TokageItLab]

• Fixes Animation tab crashing Godot 4  #72389
• Fixes Repeatable editor crash when changing between theme and animation editors #72332
• Fixes Can't open Animation tab with if a shader resource is expanded in the inspector, reverts to Shader Editor again #70705

The cause of the crash is simple recursion. Switching events bound to buttons on the bottom panel were being called recursively by inspector updates.

The inability to transition to the animation tab is due to the inspector update, which can be resolved by the restriction that bottom tab switching is allowed only once in the same frame. This means that the pending update method of #68498 cannot be used.

[KoBeWi]

This does fix the issues, but while testing I discovered a new buggy behavior (which is either exposed or caused by this PR).

1. First make sure that Animation is active (i.e. the keys are visible in the inspector)
2. Add a theme to some Control node and unfold it
3. You will see Theme editor
4. Switch to Animation tab
5. The inspector should be displaying: Control node properties, keys, unfolded theme
6. Fold Theme resource in the inspector
7. Switch to Theme editor
8. The Theme tab disappears, but the editor opens normally
9. Ghost editor 👻
   

Although I guess it's still better than being unable to switch to Animation or crashing.

[KoBeWi]

Approving, but this might be a temporary solution, or at least it requires further fixes.

[TokageItLab]

Ghost editors seem to have existed before this PR...

[TokageItLab]

This fixes the switching bug, but I found a side effect in the EditorPlugin which may spam switching in the bottom panel, may cause problems with the bottom panel closing unwillingly.

The ones I have encountered so far are SpriteFramesEditor and ThemeEditor, but they may need to be addressed individually. Also, the ghost editor has existed prior to this PR, but that may need to be fixed as well.

[akien-mga]

Thanks!

[TokageItLab]

Note: The issue with the theme editor seemed to be a different problem #72271

[JulianHeuser]

This seems to have caused another issue - I'm using a custom editor plugin that updates whenever a node is selected. However, after beta 17, the _edit function is only called if the dock updates. Previously, it would be called every time a new node was selected.

This means I have to select a node that causes my custom dock to hide, then select another node that makes it appear again to get it to update at all.

I don't see exactly how this could have been caused by this fix, but I don't see any other PRs that changed EditorPlugin since beta 16 (where everything worked as expected)