### 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 (is_inside_tree() && is_visible() && exclusive) {
			if (transient_parent->exclusive_child == nullptr) {
				if (!is_in_edited_scene_root()) {
					transient_parent->exclusive_child = this;
				}
			} else if (transient_parent->exclusive_child != this) {
				ERR_PRINT("Making child transient exclusive, but parent has another exclusive child");
			}
		}
	}
	
	if (transient_parent->window_id != DisplayServer::INVALID_WINDOW_ID && window_id != DisplayServer::INVALID_WINDOW_ID) {
		DisplayServer::get_singleton()->window_set_transient(window_id, transient_parent->window_id);
	}
}
void Window::set_transient(bool p_transient) {
	if (transient == p_transient) {
		return;
	}
	transient = p_transient;
	if (!is_inside_tree()) {
		return;
	}
	if (transient) {
		_make_transient();
	} else {
		_clear_transient();
	}
}
bool Window::is_transient() const {