script: Change signature of Event::dispatch to match the spec and simplify things (#38566)

- [Dispatch Event](https://dom.spec.whatwg.org/#concept-event-dispatch)
should return a Boolean. This function is used frequently in spec and
the change makes things easier to follow.
- Remove `enum EventStatus` and related functions.
- Update some dead spec link.
- Update some steps.

This is intended as cleanup before working on #38435 and reduces binary
size by 488KB in Release profile.

Testing: No behaviour change.

---------

Signed-off-by: Euclid Ye <euclid.ye@huawei.com>

components/script/dom/dedicatedworkerglobalscope.rs

@@ -46,7 +46,7 @@ use crate::dom::bindings::trace::{CustomTraceable, RootedTraceableBox};
 use crate::dom::bindings::utils::define_all_exposed_interfaces;
 use crate::dom::csp::{Violation, parse_csp_list_from_metadata};
 use crate::dom::errorevent::ErrorEvent;
-use crate::dom::event::{Event, EventBubbles, EventCancelable, EventStatus};
+use crate::dom::event::{Event, EventBubbles, EventCancelable};
 use crate::dom::eventtarget::EventTarget;
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::messageevent::MessageEvent;
@@ -737,11 +737,9 @@ impl DedicatedWorkerGlobalScope {
                 HandleValue::null(),
                 CanGc::note(),
             );
-            let event_status =
-                event.upcast::<Event>().fire(worker.upcast::<EventTarget>(), CanGc::note());
 
             // Step 2.
-            if event_status == EventStatus::NotCanceled {
+            if event.upcast::<Event>().fire(worker.upcast::<EventTarget>(), CanGc::note()) {
                 global.report_an_error(error_info, HandleValue::null(), CanGc::note());
             }
         }));