### 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)
if (gui.dragging) {
			
			Control *drag_preview = _gui_get_drag_preview();
			if (drag_preview) {
				drag_preview->set_position(mpos);
			}
			gui.drag_mouse_over = over;
			gui.drag_mouse_over_pos = Vector2();
			
			
			Viewport *embedder = nullptr;
			Vector2 viewport_pos;
			if (is_embedding_subwindows()) {
				embedder = this;
				viewport_pos = mpos;
			} else {
				
				Window *w = Object::cast_to<Window>(this);
				if (w) {
					if (w->is_embedded()) {
						embedder = w->_get_embedder();
						viewport_pos = get_final_transform().xform(mpos) + w->get_position(); 
					}
				}
			}
			Viewport *viewport_under = nullptr;
			if (embedder) {
				
				for (int i = embedder->gui.sub_windows.size() - 1; i >= 0; i--) {
					Window *sw = embedder->gui.sub_windows[i].window;