### Godot version

v4.0.beta17.official [c40020513]

### System information

macOS 13.0.1

### Issue description

When a `Control` node is over a `SubViewportContainer` (with a `SubViewport` as a child), both in Full Rect anchors, asking for the get_viewport().get_mouse_position() from a scene inside the `SubViewport` returns (0, 0) as the position of the mouse.

This wasn't happening in at least Beta 15. I was getting the mouse position without any problems before Beta 17. I didn't try Beta 16.

### Steps to reproduce

1. Create a `Control` node
2. Add two children: A `SubViewportContainer` and a `Control` node
3. Put both in Full Rect anchors so the `Control` node (child) is covering the `SubViewportContainer`
4. Ask for the get_viewport().get_mouse_position() from inside a scene of the `SubViewport`

As you can see in this screenshot: asking for the mouse position from inside the `Node2D` script always returns (0, 0).

<img width="1533" alt="SubViewportContainerIssue" src="https://user-images.githubusercontent.com/91340577/217051768-d9c2e8ad-40ca-4c6d-bb98-f6a7c9c6081f.png">

Only If the `Control` (child) mouse filtering is set to _Ignore_ you can get the mouse position. But with that you are losing the mouse inputs from that `Control` node.

You can find the setup of these nodes in the MRP.


### Minimal reproduction project

Run the main scene (control.tscn) and move the mouse around the screen. Look for the print in the Output tab.

[SubViewportMousePositionIssue.zip](https://github.com/godotengine/godot/files/10667894/SubViewportMousePositionIssue.zip)
max_size.x = MAX(max_size.x, 1);
					max_size.y = MAX(max_size.y, 1);
					if (r.size.x > max_size.x) {
						r.size.x = max_size.x;
					}
					if (r.size.y > max_size.y) {
						r.size.y = max_size.y;
					}
				}
				gui.subwindow_focused->_rect_changed_callback(r);
			}
			if (gui.subwindow_focused) { 
				_sub_window_update(gui.subwindow_focused);
			}
		}
		return true; 
	}
	Ref<InputEventMouseButton> mb = p_event;
	
	if (mb.is_valid() && mb->is_pressed() && mb->get_button_index() == MouseButton::LEFT) {
		bool click_on_window = false;
		for (int i = gui.sub_windows.size() - 1; i >= 0; i--) {
			SubWindow sw = gui.sub_windows.write[i];
			
			Rect2i r = Rect2i(sw.window->get_position(), sw.window->get_size());
			if (!sw.window->get_flag(Window::FLAG_BORDERLESS)) {
				
				int title_height = sw.window->get_theme_constant(SNAME("title_height"));
				Rect2i title_bar = r;
				title_bar.position.y -= title_height;