Some of the JHtml stuff will be particularly useful for rendering certain elements (unless someone has a better idea). So, port over the tracker's JHtml classes (and any non-media loading dependencies from the Platform code since that depends on JDocument). For the sake of all that is sane, let's not recreate JHtml::_(), just directly call the classes.

Component specific helpers should be in the Joomla\Tracker\Components\<component>\Html namespace and general helpers that we can recycle should be in the Joomla\Tracker\Html namespace.