style: More container queries plumbing

Provide container information in computed::Context and use it to resolve
the container queries.

This still fails a lot of tests because we are not ensuring that layout
is up-to-date when we style the container descendants, but that's
expected.

Differential Revision: https://phabricator.services.mozilla.com/D146478

components/style/dom.rs

@@ -928,6 +928,9 @@ pub trait TElement:
     /// Returns element's namespace.
     fn namespace(&self)
         -> &<SelectorImpl as selectors::parser::SelectorImpl>::BorrowedNamespaceUrl;
+
+    /// Returns the size of the primary box of the element.
+    fn primary_box_size(&self) -> euclid::default::Size2D<app_units::Au>;
 }
 
 /// TNode and TElement aren't Send because we want to be careful and explicit