Make use of match tree in HCM route table

There's a few different ways of implementing this, but the most likely one seems to be to oneof it with the existing route table implementation. There are some challenges here due to existing couplings between the route table and filter APIs, e.g.

virtual Router::RouteConstSharedPtr route(const Router::RouteCallback& cb) PURE;

, but if we can skip supporting this for the new match tree this might be relatively easy.

One open question would be to see if we want to retain the idea of virtual hosts when using the match tree since we can express the :authority lookup within the match tree.