sshpeer: use peer interface We need the same @property conversion of ui like we did for localpeer. We renamed _capabilities() to capabilities() to satisfy the new naming requirement. However, since we're inheriting from wireproto.wirepeer which inherits from peer.peerrepository and provides its own code accessing _capabilities(), we need to keep the old alias around. This wonkiness will disappear once wirepeer is cleaned up in subsequent commits. We also implement methods for basepeer that are identical to the defaults in peer.peerrepository in preparation for the removal of peerrepository. Differential Revision: https://phab.mercurial-scm.org/D336