### 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_MAIN_THREAD_GUARD;
	ERR_FAIL_NULL(p_viewport);
	ERR_FAIL_NULL(p_control);
	if (gui.mouse_focus) {
		p_viewport->gui.mouse_focus = p_control;
		p_viewport->gui.mouse_focus_mask = gui.mouse_focus_mask;
		p_viewport->gui.key_focus = p_control;
		p_viewport->gui.forced_mouse_focus = true;
		gui.mouse_focus = nullptr;
		gui.forced_mouse_focus = false;
		gui.mouse_focus_mask.clear();
	}
}
void Viewport::set_sdf_oversize(SDFOversize p_sdf_oversize) {
	ERR_MAIN_THREAD_GUARD;
	ERR_FAIL_INDEX(p_sdf_oversize, SDF_OVERSIZE_MAX);
	sdf_oversize = p_sdf_oversize;
	RS::get_singleton()->viewport_set_sdf_oversize_and_scale(viewport, RS::ViewportSDFOversize(sdf_oversize), RS::ViewportSDFScale(sdf_scale));
}
Viewport::SDFOversize Viewport::get_sdf_oversize() const {
	ERR_READ_THREAD_GUARD_V(SDF_OVERSIZE_100_PERCENT);
	return sdf_oversize;
}
void Viewport::set_sdf_scale(SDFScale p_sdf_scale) {
	ERR_MAIN_THREAD_GUARD;
	ERR_FAIL_INDEX(p_sdf_scale, SDF_SCALE_MAX);
	sdf_scale = p_sdf_scale;
	RS::get_singleton()->viewport_set_sdf_oversize_and_scale(viewport, RS::ViewportSDFOversize(sdf_oversize), RS::ViewportSDFScale(sdf_scale));
}
Viewport::SDFScale Viewport::get_sdf_scale() const {