Synchronize dispatch_actions in WebDriver (#36932)

Implement missing synchronization in `dispatch_actions` of `WebDriver`.
https://w3c.github.io/webdriver/#dispatching-actions

> The user agent event loop has spun enough times to process the DOM
events generated by the last invocation of the >[dispatch tick
actions](https://w3c.github.io/webdriver/#dfn-dispatch-tick-actions)
steps.

- Add a way for `ScriptThread` to notify `WebDriver` about the
completion of input commands.
- Add a `webdriver_id` field for `InputEvent`. `ScriptThread` uses it to
distinguish WebDriver events and sends notification.

Tests:
`./mach test-wpt --product servodriver -r
tests\wpt\tests\webdriver\tests\classic\element_click\events.py` pass if
`hit_testing` pass. Check
[issue](https://github.com/servo/servo/issues/36676#issuecomment-2882917136)

cc: @xiaochengh

---------

Signed-off-by: batu_hoang <longvatrong111@gmail.com>
Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Martin Robinson <mrobinson@igalia.com>

ports/servoshell/desktop/headed_window.rs

@@ -262,11 +262,11 @@ impl Window {
             ElementState::Released => MouseButtonAction::Up,
         };
 
-        webview.notify_input_event(InputEvent::MouseButton(MouseButtonEvent {
+        webview.notify_input_event(InputEvent::MouseButton(MouseButtonEvent::new(
             action,
-            button: mouse_button,
+            mouse_button,
             point,
-        }));
+        )));
     }
 
     /// Handle key events before sending them to Servo.
@@ -563,7 +563,7 @@ impl WindowPortsMethods for Window {
                 point.y -= (self.toolbar_height() * self.hidpi_scale_factor()).0;
 
                 self.webview_relative_mouse_point.set(point);
-                webview.notify_input_event(InputEvent::MouseMove(MouseMoveEvent { point }));
+                webview.notify_input_event(InputEvent::MouseMove(MouseMoveEvent::new(point)));
             },
             WindowEvent::MouseWheel { delta, phase, .. } => {
                 let (mut dx, mut dy, mode) = match delta {