script: Expose node helpers as NodeTraits and give more descriptive names (#34832)

This puts a few commonly used `Node` helpers into a trait (`NodeTraits`)
and gives them more descriptive names and documentation. The renames:

- `document_from_node` -> `NodeTraits::owner_document`
- `window_from_node` -> `NodeTraits::owner_window`
- `stylesheets_owner_from_node<T:` -> `NodeTraits::stylesheet_list_owner`
- `containing_shadow_root` -> `NodeTraits::containing_shadow_root`

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

components/script/dom/domtokenlist.rs

@@ -14,7 +14,7 @@ use crate::dom::bindings::reflector::{reflect_dom_object, Reflector};
 use crate::dom::bindings::root::{Dom, DomRoot};
 use crate::dom::bindings::str::DOMString;
 use crate::dom::element::Element;
-use crate::dom::node::window_from_node;
+use crate::dom::node::NodeTraits;
 use crate::script_runtime::CanGc;
 
 #[dom_struct]
@@ -46,14 +46,13 @@ impl DOMTokenList {
         local_name: &LocalName,
         supported_tokens: Option<Vec<Atom>>,
     ) -> DomRoot<DOMTokenList> {
-        let window = window_from_node(element);
         reflect_dom_object(
             Box::new(DOMTokenList::new_inherited(
                 element,
                 local_name.clone(),
                 supported_tokens,
             )),
-            &*window,
+            &*element.owner_window(),
             CanGc::note(),
         )
     }