script: Expose NodeTraits::owner_global / Window::as_global_scope (#34843)

Expose two new helpers and start using them as much as possible.

- `NodeTraits::owner_global`: which gets the `GlobalScope` that currenty
 owns a `Node`. This may be different than `.global()` in the case that
 the `Node` was adopted by a different `Document`.
- `Window::as_global_scope`: A helper to avoid having to cast so much
  when treating a `Window` like a `GlobalScope`.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

components/script/dom/analysernode.rs

@@ -111,6 +111,7 @@ impl AnalyserNode {
         let (node, recv) = AnalyserNode::new_inherited(window, context, options)?;
         let object = reflect_dom_object_with_proto(Box::new(node), window, proto, can_gc);
         let task_source = window
+            .as_global_scope()
             .task_manager()
             .dom_manipulation_task_source()
             .to_sendable();