Report exceptions for async script executions to webdriver (#27041)

Improving the accuracy of the async script execution for our webdriver
implementation allows us to run many more webdriver tests without
timeouts, which should help with
https://github.com/web-platform-tests/wpt/issues/24257.

Specification:
* https://w3c.github.io/webdriver/#dfn-clone-an-object
* https://w3c.github.io/webdriver/#execute-async-script

---
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #27036 and fix #27035 and fix #27031.
- [x] There are tests for these changes (but we don't run them in CI
yet)

---------

Signed-off-by: Josh Matthews <josh@joshmatthews.net>

components/shared/embedder/webdriver.rs

@@ -170,6 +170,7 @@ pub enum WebDriverJSError {
     /// Occurs when handler received an event message for a layout channel that is not
     /// associated with the current script thread
     BrowsingContextNotFound,
+    JSException(WebDriverJSValue),
     JSError,
     StaleElementReference,
     Timeout,