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/constellation/tracing.rs

@@ -177,6 +177,7 @@ mod from_script {
                 Self::TitleChanged(..) => target!("TitleChanged"),
                 Self::IFrameSizes(..) => target!("IFrameSizes"),
                 Self::ReportMemory(..) => target!("ReportMemory"),
+                Self::WebDriverInputComplete(..) => target!("WebDriverInputComplete"),
                 Self::FinishJavaScriptEvaluation(..) => target!("FinishJavaScriptEvaluation"),
             }
         }