MediaRouter: make route controllers return route info

Since RouteSessionInfo holds lists of route ids which are unique
only in a provider, ids returned by RouteSessionController can't be
used to identify routes from different providers.

Using provider id in the route session together, route controller
can return route infos that can be used directly by end users.

Test: atest mediaroutertest
Change-Id: I0dbbae2b66f5c1c77c9a9b624fcf924c9e1a280a