### 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_FAIL_COND(p_event.is_null());
	Ref<InputEventMouseButton> mb = p_event;
	if (mb.is_valid()) {
		if (!mb->is_pressed()) {
			gui.mouse_focus_mask.clear_flag(mouse_button_to_mask(mb->get_button_index())); 
		}
	}
}
List<Control *>::Element *Viewport::_gui_add_root_control(Control *p_control) {
	gui.roots_order_dirty = true;
	return gui.roots.push_back(p_control);
}
void Viewport::gui_set_root_order_dirty() {
	ERR_MAIN_THREAD_GUARD;
	gui.roots_order_dirty = true;
}
void Viewport::_gui_force_drag(Control *p_base, const Variant &p_data, Control *p_control) {
	ERR_FAIL_COND_MSG(p_data.get_type() == Variant::NIL, "Drag data must be a value.");
	gui.dragging = true;
	gui.drag_data = p_data;
	gui.mouse_focus = nullptr;
	if (p_control) {
		_gui_set_drag_preview(p_base, p_control);
	}
	_propagate_viewport_notification(this, NOTIFICATION_DRAG_BEGIN);
}
void Viewport::_gui_set_drag_preview(Control *p_base, Control *p_control) {