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/script/dom/window.rs

@@ -1216,15 +1216,26 @@ impl WindowMethods<crate::DomTypeHolder> for Window {
         }
     }
 
-    #[allow(unsafe_code)]
-    fn WebdriverCallback(&self, cx: JSContext, val: HandleValue) {
-        let rv = unsafe { jsval_to_webdriver(*cx, &self.globalscope, val) };
+    fn WebdriverCallback(&self, cx: JSContext, val: HandleValue, realm: InRealm, can_gc: CanGc) {
+        let rv = jsval_to_webdriver(cx, &self.globalscope, val, realm, can_gc);
         let opt_chan = self.webdriver_script_chan.borrow_mut().take();
         if let Some(chan) = opt_chan {
             chan.send(rv).unwrap();
         }
     }
 
+    fn WebdriverException(&self, cx: JSContext, val: HandleValue, realm: InRealm, can_gc: CanGc) {
+        let rv = jsval_to_webdriver(cx, &self.globalscope, val, realm, can_gc);
+        let opt_chan = self.webdriver_script_chan.borrow_mut().take();
+        if let Some(chan) = opt_chan {
+            if let Ok(rv) = rv {
+                chan.send(Err(WebDriverJSError::JSException(rv))).unwrap();
+            } else {
+                chan.send(rv).unwrap();
+            }
+        }
+    }
+
     fn WebdriverTimeout(&self) {
         let opt_chan = self.webdriver_script_chan.borrow_mut().take();
         if let Some(chan) = opt_chan {