### 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)
Ref<InputEventMouseMotion> mm = p_event;
		if (mm.is_valid()) {
			if (gui.subwindow_drag == SUB_WINDOW_DRAG_MOVE) {
				Vector2 diff = mm->get_position() - gui.subwindow_drag_from;
				Rect2i new_rect(gui.subwindow_drag_pos + diff, gui.subwindow_focused->get_size());
				if (gui.subwindow_focused->is_clamped_to_embedder()) {
					Size2i limit = get_visible_rect().size;
					if (new_rect.position.x + new_rect.size.x > limit.x) {
						new_rect.position.x = limit.x - new_rect.size.x;
					}
					if (new_rect.position.y + new_rect.size.y > limit.y) {
						new_rect.position.y = limit.y - new_rect.size.y;
					}
					if (new_rect.position.x < 0) {
						new_rect.position.x = 0;
					}
					int title_height = gui.subwindow_focused->get_flag(Window::FLAG_BORDERLESS) ? 0 : gui.subwindow_focused->get_theme_constant(SNAME("title_height"));
					if (new_rect.position.y < title_height) {
						new_rect.position.y = title_height;
					}
				}
				gui.subwindow_focused->_rect_changed_callback(new_rect);
			}
			if (gui.subwindow_drag == SUB_WINDOW_DRAG_CLOSE) {
				gui.subwindow_drag_close_inside = gui.subwindow_drag_close_rect.has_point(mm->get_position());
			}
			if (gui.subwindow_drag == SUB_WINDOW_DRAG_RESIZE) {
				Vector2i diff = mm->get_position() - gui.subwindow_drag_from;
				Size2i min_size = gui.subwindow_focused->get_min_size();
				Size2i min_size_adjusted = min_size;