script: Reduce usage of Trusted in Node::insert. (#37762)

These changes introduce a new kind of task that uses a variation of the
`task!` syntax. Existing `task!` usages create task structs that have a
`Send` bound, which requires the use of `Trusted<T>` to reference a DOM
object T inside of the task closure. The new syntax replaces the `Send`
bound with a `JSTraceable` bound, which requires explicit capture
clauses with types. This looks like:
```rust
task!(ScriptPrepare: {script: DomRoot<HTMLScriptElement>} |script| {
    script.prepare(CanGc::note());
}),
```

The capture clauses must list every value that will be referenced from
the closure's environment—these values are moved into fields in the
generated task structure, which allows them to be traced by the GC as
part of a generated JSTraceable implementation. Since the closure itself
is not a `move` closure, any attempts to reference values not explicitly
captured will generate a borrow checker error since the closure requires
the `'static` lifetime.

Testing: Existing WPT tests exercise these code paths. I also attempted
to write incorrect tasks that capture references or use values not
explicitly captured, and the compiler correctly errors out.
Fixes: part of #35517

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

components/script/dom/htmlscriptelement.rs

@@ -1414,15 +1414,15 @@ impl VirtualMethods for HTMLScriptElement {
         }
 
         if self.upcast::<Node>().is_connected() && !self.parser_inserted.get() {
-            let script = Trusted::new(self);
+            let script = DomRoot::from_ref(self);
             // This method can be invoked while there are script/layout blockers present
             // as DOM mutations have not yet settled. We use a delayed task to avoid
             // running any scripts until the DOM tree is safe for interactions.
-            self.owner_document()
-                .add_delayed_task(task!(ScriptPrepare: move || {
-                    let this = script.root();
-                    this.prepare(CanGc::note());
-                }));
+            self.owner_document().add_delayed_task(
+                task!(ScriptPrepare: |script: DomRoot<HTMLScriptElement>| {
+                    script.prepare(CanGc::note());
+                }),
+            );
         }
     }