### 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_READ_THREAD_GUARD_V(nullptr);
	return camera_2d;
}
Transform2D Viewport::get_final_transform() const {
	ERR_READ_THREAD_GUARD_V(Transform2D());
	return stretch_transform * global_canvas_transform;
}
void Viewport::assign_next_enabled_camera_2d(const StringName &p_camera_group) {
	ERR_MAIN_THREAD_GUARD;
	List<Node *> camera_list;
	get_tree()->get_nodes_in_group(p_camera_group, &camera_list);
	Camera2D *new_camera = nullptr;
	for (Node *E : camera_list) {
		Camera2D *cam = Object::cast_to<Camera2D>(E);
		if (!cam) {
			continue; 
		}
		if (cam->is_enabled()) {
			new_camera = cam;
			break;
		}
	}
	_camera_2d_set(new_camera);
	if (!camera_2d) {
		set_canvas_transform(Transform2D());
	}
}
void Viewport::_update_canvas_items(Node *p_node) {