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/debuggerglobalscope.rs

@@ -24,7 +24,6 @@ use crate::dom::bindings::inheritance::Castable;
 use crate::dom::bindings::root::DomRoot;
 use crate::dom::bindings::trace::CustomTraceable;
 use crate::dom::bindings::utils::define_all_exposed_interfaces;
-use crate::dom::event::EventStatus;
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::types::{DebuggerEvent, Event};
 #[cfg(feature = "testbinding")]
@@ -124,10 +123,9 @@ impl DebuggerGlobalScope {
     }
 
     pub(crate) fn fire_add_debuggee(&self, can_gc: CanGc, global: &GlobalScope) {
-        assert_eq!(
+        assert!(
             DomRoot::upcast::<Event>(DebuggerEvent::new(self.upcast(), global, can_gc))
                 .fire(self.upcast(), can_gc),
-            EventStatus::NotCanceled,
             "Guaranteed by DebuggerEvent::new"
         );
     }