### 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.
embedder->_sub_window_register(this);
			RS::get_singleton()->viewport_set_update_mode(get_viewport_rid(), RS::VIEWPORT_UPDATE_WHEN_PARENT_VISIBLE);
		} else {
			embedder->_sub_window_remove(this);
			embedder = nullptr;
			RS::get_singleton()->viewport_set_update_mode(get_viewport_rid(), RS::VIEWPORT_UPDATE_DISABLED);
		}
		_update_window_size();
	}
	if (!visible) {
		focused = false;
	}
	notification(NOTIFICATION_VISIBILITY_CHANGED);
	emit_signal(SceneStringNames::get_singleton()->visibility_changed);
	RS::get_singleton()->viewport_set_active(get_viewport_rid(), visible);
	
	if (transient_parent) {
		if (exclusive && visible) {
			if (!is_in_edited_scene_root()) {
				ERR_FAIL_COND_MSG(transient_parent->exclusive_child && transient_parent->exclusive_child != this, "Transient parent has another exclusive child.");
				transient_parent->exclusive_child = this;
			}
		} else {
			if (transient_parent->exclusive_child == this) {
				transient_parent->exclusive_child = nullptr;
			}
		}
	}
}
void Window::_clear_transient() {