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>

components/shared/compositing/lib.rs

@@ -10,6 +10,7 @@ use base::id::{PipelineId, WebViewId};
 use crossbeam_channel::Sender;
 use embedder_traits::{
     AnimationState, EventLoopWaker, MouseButton, MouseButtonAction, TouchEventResult,
+    WebDriverMessageId,
 };
 use euclid::Rect;
 use ipc_channel::ipc::IpcSender;
@@ -101,9 +102,16 @@ pub enum CompositorMsg {
     /// The load of a page has completed
     LoadComplete(WebViewId),
     /// WebDriver mouse button event
-    WebDriverMouseButtonEvent(WebViewId, MouseButtonAction, MouseButton, f32, f32),
+    WebDriverMouseButtonEvent(
+        WebViewId,
+        MouseButtonAction,
+        MouseButton,
+        f32,
+        f32,
+        WebDriverMessageId,
+    ),
     /// WebDriver mouse move event
-    WebDriverMouseMoveEvent(WebViewId, f32, f32),
+    WebDriverMouseMoveEvent(WebViewId, f32, f32, WebDriverMessageId),
     // Webdriver wheel scroll event
     WebDriverWheelScrollEvent(WebViewId, f32, f32, f64, f64),