### 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.
Vector2 viewport_pos;
			if (is_embedding_subwindows()) {
				embedder = this;
				viewport_pos = mpos;
			} else {
				
				Window *w = Object::cast_to<Window>(this);
				if (w) {
					if (w->is_embedded()) {
						embedder = w->get_embedder();
						viewport_pos = get_final_transform().xform(mpos) + w->get_position(); 
					}
				}
			}
			Viewport *viewport_under = nullptr;
			if (embedder) {
				
				for (int i = embedder->gui.sub_windows.size() - 1; i >= 0; i--) {
					Window *sw = embedder->gui.sub_windows[i].window;
					Rect2 swrect = Rect2i(sw->get_position(), sw->get_size());
					if (!sw->get_flag(Window::FLAG_BORDERLESS)) {
						int title_height = sw->get_theme_constant(SNAME("title_height"));
						swrect.position.y -= title_height;
						swrect.size.y += title_height;
					}
					if (swrect.has_point(viewport_pos)) {
						viewport_under = sw;
						viewport_pos -= sw->get_position();
					}
				}