Construction of the highlight containers was moved to the backend, but
setupHighlightContainers() also aggregates the CSS classes used for
highlights for grouped entries in enhanced mode.
Move that to the backend too, and get rid of setupHighlightContainers().
Also move the namespace classes to getHTMLClassesForFilters() so that
they get picked up too, and pick up classes for tags separately because
the way they're handled is weird.
Bug: T197168
Change-Id: I4c374f82e7d128025f4e2b2f39b0adba14b76ef3
39163edd17