GodotString in virtual method parameters crash godot unless forgotten

[lilizoey]

When implementing a virtual method that has a GodotString as a parameter, you need to do std::mem::forget() on that parameter, otherwise godot will crash.

Example of implementing ScriptLanguageExtensionVirtual::validate_path:

// additional validation on file-paths, return empty string for no error
fn validate_path(&self, path: GodotString) -> GodotString {
    println!("extension validate_path");
    std::mem::forget(path);
    GodotString::from("")
}

im here also adding a custom patch to gdextension where i just add in the return types for virtual methods (because of #190). it's fairly fragile and has some issues atm. but shouldn't interfere with this issue at hand, might clean that patch up at some point and upstream it.

[lilizoey]

this also happens with pointer calls in general it seems