Rename #[godot] to #[method]

[Bromeon]

Follow-up to #872.

As mentioned there, the syntax was provisional and still subject to change. This PR renames #[godot] back to #[method].
Other changes, such as the #[base] parameter name, remain unaffected (still a bit conflicted about that too, but that's another story...)

Reasoning behind the name #[godot] was a potential greater unification of godot-rust attributes, which would allow to use #[godot] more widespread as the attribute, e.g.

#[derive(NativeClass)]
#[godot(inherit=Node, no_constructor)]
struct MyClass {
    #[godot(get)]
    my_property: i32,
}

#[godot_api]
impl MyClass {
    #[godot]
    fn my_method(&self, #[base] base: &Node) {...}
}

However, this comes with a bigger change. In order to avoid huge deprecations or breaking changes, I think it makes sense to not include this in the current minor version. It could be discussed for v0.11, or maybe only for GDExtension. Since having #[godot] in only one place would be "somewhere in between" the old and new naming, I'd rather find an identifier that fits the existing #[property] and #[methods] naming scheme -- and #[method] as suggested by the original author would fit relatively nicely.

Overall, I still believe "method" is not expressive and there is room for improvement, as well as for other names like "property" or so. But I don't want this to delay the whole 0.10.1 release further; we'd rather think about nicer naming another time, maybe when GDExtension is around.

This PR introduces a breaking change toward master, but not toward the last released version 0.10.0, so it can be included in 0.10.1.

[Bromeon]

bors try

[bors]

try

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[Bromeon]

bors r+

[bors]

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[Bromeon]

bors r+

[bors]

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