Generated enum getters and setters should return the enum type in Rust

[jsternberg]

When creating an enum such as the following:

#[derive(GodotConvert, Var, Export, Clone, Copy)]
#[godot(via = u8)]
pub enum WeaponType {
    Axe,
    Sword,
    Lance,
}

If you then use the enum as an export/var.

#[derive(GodotClass)]
#[class(init, base=Node)]
pub struct MyCustomNode {
    base: Base<Node>,
    #[export]
    weapon_type: WeaponType,
}

The generated getter and setter for this uses the Via type instead of the enum. This results in the following code getting sprinkled around in Rust.

let weapon_type = MyCustomNode::from_godot(my_node.bind().get_weapon_type());

This can be a lot to type from an ergonomics perspective. It would be nice if there was a way to have the getters and setters use the enum type directly instead of the <T as GodotConvert>::Via type or to have some alternative method or way to go about writing the above.

[Bromeon]

The get_x/set_x methods were generated originally because we needed a callback for Godot and it was the easiest, and at the time it looked like making them public is a good idea because Godot already has access to the field (and so does GDScript property access syntax). And it probably comes in handy in many cases, but I'm not 100% sure if it was the right decision. This issue for example shows that it's a leaky abstraction because it requires going through Via.

In general, getter/setter semantics will slightly change as a result of #1264, we might also rethink this.