### 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 (!p_node->is_visible()) {
		return nullptr; 
	}
	Transform2D matrix = p_xform * p_node->get_transform();
	
	if (matrix.basis_determinant() == 0.0f) {
		return nullptr;
	}
	Control *c = Object::cast_to<Control>(p_node);
	if (!c || !c->is_clipping_contents() || c->has_point(matrix.affine_inverse().xform(p_global))) {
		for (int i = p_node->get_child_count() - 1; i >= 0; i--) {
			CanvasItem *ci = Object::cast_to<CanvasItem>(p_node->get_child(i));
			if (!ci || ci->is_set_as_top_level()) {
				continue;
			}
			Control *ret = _gui_find_control_at_pos(ci, p_global, matrix);
			if (ret) {
				return ret;
			}
		}
	}
	if (!c || c->data.mouse_filter == Control::MOUSE_FILTER_IGNORE) {
		return nullptr;
	}
	matrix.affine_invert();
	if (!c->has_point(matrix.xform(p_global))) {
		return nullptr;
	}
	Control *drag_preview = _gui_get_drag_preview();