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/domstringmap.rs

@@ -10,7 +10,7 @@ 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::htmlelement::HTMLElement;
-use crate::dom::node::window_from_node;
+use crate::dom::node::NodeTraits;
 use crate::script_runtime::CanGc;
 
 #[dom_struct]
@@ -28,10 +28,9 @@ impl DOMStringMap {
     }
 
     pub fn new(element: &HTMLElement) -> DomRoot<DOMStringMap> {
-        let window = window_from_node(element);
         reflect_dom_object(
             Box::new(DOMStringMap::new_inherited(element)),
-            &*window,
+            &*element.owner_window(),
             CanGc::note(),
         )
     }