Add fallback argument hints for default values

[bitwise-aiden]

Closes: #78191

In lieu of having constexpr, this solution proposes a fallback to provide a better hint to developers about what the default value of a method is.

I've used a similar approach to generating a default as GDScriptDocGen::_docvalue_from_variant, but assuming recursion depth is always met.

This provides value to developers by now being able to know if there is an array to be expected and if it is empty or not at a glance instead of going to look at the source for a method.

It could possibly be extended a little to include a small recursion depth, but I think that this is a good first step towards QOL.

Screen.Recording.2024-02-11.at.10.08.38.AM.mov

^ All forms of defaults are now in line with how constant and variable defaults are created.

[dalexeev]

Looks good to me. In the future we may replace _docvalue_from_variant() with a hint_from_expression() and use this in both DocGen and the editor, but for now it looks like a small and fine change.

[akien-mga]

Thanks! And congrats for your first merged Godot contribution 🎉

[bitwise-aiden]

In the future we may replace _docvalue_from_variant() with a hint_from_expression() and use this in both DocGen and the editor

When I get the chance I'll have a look into it.

Thanks! And congrats for your first merged Godot contribution 🎉

Thank you! First of many I hope ;p