This commit changes the bounds on the path selection helper methods
`best` and `best_backup` to ensure we have access to the actual OrdRoute
contents. Those are necessary for comparison of the actual route
contents (path attributes, additional tiebreaker info), specifically in
`best_backup`. Before, those methods would take the more generic `T:
Ord`, but we need to make sure any returned backup route is actually
different from the returned best route, hence the need to access the
inner values of OrdRoute.