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/embedder/webdriver.rs

@@ -24,6 +24,9 @@ use webrender_api::units::DeviceIntSize;
 
 use crate::{MouseButton, MouseButtonAction};
 
+#[derive(Clone, Copy, Debug, Deserialize, PartialEq, Serialize)]
+pub struct WebDriverMessageId(pub usize);
+
 /// Messages to the constellation originating from the WebDriver server.
 #[derive(Debug, Deserialize, Serialize)]
 pub enum WebDriverCommandMsg {
@@ -41,9 +44,23 @@ pub enum WebDriverCommandMsg {
     /// Act as if keys were pressed or release in the browsing context with the given ID.
     KeyboardAction(BrowsingContextId, KeyboardEvent),
     /// Act as if the mouse was clicked in the browsing context with the given ID.
-    MouseButtonAction(WebViewId, MouseButtonAction, MouseButton, f32, f32),
+    MouseButtonAction(
+        WebViewId,
+        MouseButtonAction,
+        MouseButton,
+        f32,
+        f32,
+        WebDriverMessageId,
+        IpcSender<WebDriverCommandResponse>,
+    ),
     /// Act as if the mouse was moved in the browsing context with the given ID.
-    MouseMoveAction(WebViewId, f32, f32),
+    MouseMoveAction(
+        WebViewId,
+        f32,
+        f32,
+        WebDriverMessageId,
+        IpcSender<WebDriverCommandResponse>,
+    ),
     /// Act as if the mouse wheel is scrolled in the browsing context given the given ID.
     WheelScrollAction(WebViewId, f32, f32, f64, f64),
     /// Set the window size.
@@ -188,6 +205,11 @@ pub enum WebDriverFrameId {
     Parent,
 }
 
+#[derive(Debug, Deserialize, Serialize)]
+pub struct WebDriverCommandResponse {
+    pub id: WebDriverMessageId,
+}
+
 #[derive(Debug, Deserialize, Serialize)]
 pub enum WebDriverLoadStatus {
     Complete,