### Godot version

v4.1.1.stable.official [bd6af8e0e]

### System information

Godot v4.1.1.stable - Debian GNU/Linux trixie/sid trixie - Vulkan (Forward+) - dedicated NVIDIA GeForce GTX 1060 (nvidia) - Intel(R) Core(TM) i5-8400 CPU @ 2.80GHz (6 Threads)

### Issue description

`Area2D`s which extend beyond the bounds of the root viewport, eg. when using a `canvas_items` stretch mode, receive mouse input events even in the black bands letterboxing the game:

https://github.com/godotengine/godot/assets/441188/3beb962f-c1fa-4098-a375-f3d862013577


### Steps to reproduce

1. Set project stretch mode to either `canvas_items` or `viewport`
2. Have an `Area2D` whose `CollisionShape` extends beyond the bounds of the rendered region
3. Connect the `Area2D`'s `mouse_[entered|exited]` signal to something
4. Wave the mouse around in the black areas outside the rendered game

### Minimal reproduction project

Project used for video demo above:

[area2d-oob.zip](https://github.com/godotengine/godot/files/12207031/area2d-oob.zip)

This only demos `mouse_[entered|exited]`, but I first encountered this with the `Area2D.input_event` signal, where it received mouse clicks as well.
ERR_MAIN_THREAD_GUARD;
	ERR_FAIL_INDEX(p_flag, FLAG_MAX);
	flags[p_flag] = p_enabled;
	if (embedder) {
		embedder->_sub_window_update(this);
	} else if (window_id != DisplayServer::INVALID_WINDOW_ID) {
		if (!is_in_edited_scene_root()) {
			DisplayServer::get_singleton()->window_set_flag(DisplayServer::WindowFlags(p_flag), p_enabled, window_id);
		}
	}
}
bool Window::get_flag(Flags p_flag) const {
	ERR_READ_THREAD_GUARD_V(false);
	ERR_FAIL_INDEX_V(p_flag, FLAG_MAX, false);
	if (window_id != DisplayServer::INVALID_WINDOW_ID) {
		if (!is_in_edited_scene_root()) {
			flags[p_flag] = DisplayServer::get_singleton()->window_get_flag(DisplayServer::WindowFlags(p_flag), window_id);
		}
	}
	return flags[p_flag];
}
bool Window::is_maximize_allowed() const {
	ERR_READ_THREAD_GUARD_V(false);
	if (window_id != DisplayServer::INVALID_WINDOW_ID) {
		return DisplayServer::get_singleton()->window_is_maximize_allowed(window_id);
	}
	return true;
}
void Window::request_attention() {