fix Option<Self> in function/method parameters and returns

[selaux]

Currently when registering a type that has methods that take or return Option<Self> in a Definition, we get a stack overflow, because it will call Ty::ty() in an infinite recursion loop. This should fix this case.

I also added some tests, but they are a little convoluted, as I couldn't find a really good way to test this. Feel free to make suggestions how to adapt or edit directly.

[Tired-Fox]

@selaux

Good catch, this was a bit of an oversite on my part and I missed this happening when I added as_param and as_return. The recursion happens as follows:

Assume there is a struct Custom that implements Typed with the ty() function returning a class type and TypedUserData that adds some function that has a param or return type of Option<Self>

1. Custom::ty()
2. TypedUserData::add_methods(...)
3. methods.add_function("test", |_, _: ()| { Ok(Some(Self)) })
4. Option::<Self>::as_return() <- Recursion happens here based on the impl of this function
5. Self::ty() <- Recursion

The test may seem like it has a lot of setup, but it seems correct.

[Tired-Fox]

I also think it could happen with Arc, Mutex, etc. This would be the case if userdata-wrapper was enabled for those wrapper types.

This PR can focus on fixing the Option case. I can create another PR for the rest