webdriver: improve perform pointermove & wheel actions with more accurate coordinates (#38095)

1. Create `get_origin_relative_coordinates` according to
[spec](https://w3c.github.io/webdriver/#dfn-get-coordinates-relative-to-an-origin)
to be reused
2. Add previously missing offset for PointerOrigin::Element
3. Refactor code for perform pointermove/wheel to be closer to spec.
4. Handle some issues with spec:
https://github.com/w3c/webdriver/issues/1758

Testing: Several new passing cases as we are more precise with
coordinates now.
Fixes: Part of #38042.

---------

Signed-off-by: Euclid Ye <euclid.ye@huawei.com>

ports/servoshell/desktop/app.rs

@@ -560,7 +560,7 @@ impl App {
                             ScrollLocation::Delta(Vector2D::new(dx as f32, dy as f32));
 
                         webview.notify_input_event(
-                            InputEvent::Wheel(WheelEvent::new(delta, point))
+                            InputEvent::Wheel(WheelEvent::new(delta, point.to_f32()))
                                 .with_webdriver_message_id(webdriver_message_id),
                         );