### 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.
if (is_embedding_subwindows()) {
		for (int i = gui.sub_windows.size() - 1; i >= 0; i--) {
			Window *sw = gui.sub_windows[i].window;
			Rect2 swrect = Rect2(sw->get_position(), sw->get_size());
			Rect2 swrect_border = swrect;
			if (!sw->get_flag(Window::FLAG_BORDERLESS)) {
				int title_height = sw->get_theme_constant(SNAME("title_height"));
				int margin = sw->get_theme_constant(SNAME("resize_margin"));
				swrect_border.position.y -= title_height + margin;
				swrect_border.size.y += title_height + margin * 2;
				swrect_border.position.x -= margin;
				swrect_border.size.x += margin * 2;
			}
			if (swrect_border.has_point(p_pos)) {
				if (gui.mouse_over) {
					_drop_mouse_over();
				} else if (!gui.subwindow_over) {
					_drop_physics_mouseover();
				}
				if (swrect.has_point(p_pos)) {
					if (sw != gui.subwindow_over) {
						if (gui.subwindow_over) {
							gui.subwindow_over->_mouse_leave_viewport();
						}