Eradicate optional Variant

[elijah-semyonov]

Change API to reflect nullability as an intrinsic part of Variant semantics to avoid awkward states like Variant? containing .some(Variant) containing Godot Nil.

[migueldeicaza]

You have some enthusiastic comments on Slack during your code review that lead to this, would love to know more about those.

generally, being a breaking change I am a bit concerned about this, but also losing the language support. An alternative is going the other way, but as I mentioned on slack, that could lead to an impedance mismatch.

so I think it would be good to explore the pros and cons in depth before crossing either bridge

[elijah-semyonov]

I'll cook the opposite approach and try to amalgamate Godot Nil into Swift nil.