Add DebugLabel node

[Xrayez]

Helps godotengine/godot-proposals#115.

A label which displays a list of property values in any Object instance, suitable for both in-game and editor debugging of nodes.

The implementation is fairly straightforward. I've done some attempts on color coding variant types with RichTextLabel but there are usability issues with having to set minimum size manually for each label for the contents to be displayed.

Re-implementing the internal Label functionality just to achieve this seamless display of text with custom colors seems like an arduous task to do via script currently. Even if one manages to draw stuff with font.draw_char or draw_string, there are still many aspects to account like font character spacing, line spacing etc. var2str is used over String() conversion which converts any Variant to text in a consistent way at least (and can even be parsed back with str2var if you manage to copy-paste the debug label contents, which is possible in RichTextLabel btw).

Works in 3.1 and 3.2.

Test project

godot-debug-label.zip

[willnationsdev]

@Xrayez Thanks!