Implement export_multiline support for Array[String] and Dictionary

[vaartis]

For arrays, specifically check if it's a string array and pass the type on to the editor. For dictionaries, save the hint on the type and use it later to draw the multiline editor, except for when adding a string key, because that doesn't make much sense. All string values however will be drawn as multiline.

Closes #62011

[vnen]

The GDScript changes are good. I can't tell much about the editor part.

[akien-mga]

Thanks! And congrats for your first merged Godot contribution 🎉