Core: Bind and document iterator API virtual methods

[dalexeev]

• Resolves Remove function argument for custom iterators in GDScript godot-proposals#5096.

This is documented here, but I think it's not enough. This is one of Godot's secret features. Binding and documentation facilitates better discoverability, autocompletion, and static checks. See also #89639, the bug still exists only because it is not obvious that the _iter_get() argument does not have Array wrapper, unlike _iter_init() and _iter_next().

[dalexeev]

The name iter comes from here. I was thinking about binding this as state, but not sure.

godot/core/variant/variant.h

Lines 728 to 730 in fe01776

	bool iter_init(Variant &r_iter, bool &r_valid) const;
	bool iter_next(Variant &r_iter, bool &r_valid) const;
	Variant iter_get(const Variant &r_iter, bool &r_valid) const;

[mhilbrunner]

Documentation looks good to me.

[Mickeon]

I hope @dalexeev knows the documentation part is fine by me, too.

[dalexeev]

Since in my opinion this is a simple, small, but useful addition and since there are two approvals, I moved milestone to 4.4.

[akien-mga]

Thanks!