### 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.
#ifndef _3D_DISABLED
	if (use_xr) {
		if (XRServer::get_singleton() != nullptr) {
			Ref<XRInterface> xr_interface = XRServer::get_singleton()->get_primary_interface();
			if (xr_interface.is_valid() && xr_interface->is_initialized()) {
				Size2 xr_size = xr_interface->get_render_target_size();
				return (Size2i)xr_size;
			}
		}
		return Size2i();
	}
#endif 
	return size;
}
Size2i Viewport::_get_size_2d_override() const {
	return size_2d_override;
}
bool Viewport::_is_size_allocated() const {