Set a default text for Control nodes (and Label3D) when created in the editor

[Calinou]

This allows for immediate visual feedback when adding Control nodes in the editor. A minimum size is also set for controls that don't resize according to their text, so that the text can be displayed without wrapping, even when placed in a Container.

For compatibility, this does not affect nodes created through code (in a @tool script or otherwise).

• This closes Add default text to controls when adding Control-derived nodes (and Label3D) in the editor godot-proposals#14750.

Preview

Top: nodes added in master in an HBoxContainer. (The first node is a ColorPickerButton.)
Bottom: nodes added in this PR in an HBoxContainer.

TODO

• Consider moving the naming logic to affect any Node, not just Control and Label3D, so that nodes like Window and FileDialog can have titles set automatically.
• Add a virtual method in Control to get a default minimum size to apply in the editor, so that we don't have to hardcode exceptions here. This would also be more friendly to plugins.
• Read the theme font and scale the minimum sizes accordingly using TextServer methods.
  • If this is not feasible because the node isn't created yet, use the default theme scale from the Project Settings to multiply the values.

[Calinou]

I've changed the size thresholds for default sizing as the current threshold of (4, 4) didn't catch nodes like TextEdit. I assume this occurs because the current values were set a long time ago, when the default project theme was targeting lower resolutions than today.

[KoBeWi]

Add a virtual method in Control to get a default minimum size to apply in the editor, so that we don't have to hardcode exceptions here. This would also be more friendly to plugins.

Something like #81217 could be suitable here.

[KoBeWi]

This should be

Suggested change

	if (Object::cast_to<ColorPickerButton>(control)) {
	ColorPickerButton *color_picker_button = Object::cast_to<ColorPickerButton>(control);
	if (color_picker_button) {

Then you can use the setter directly instead of using set().

EDIT:
Just like you did for Label3D...

[Calinou]

There are a lot of controls with text or title properties, so I'd need to check for them individually if I wanted to use a typed approach.