wireprotoserver: make name part of protocol interface This is a required part of the interface. Abstract properties must be defined at type creation time. So we make name a @property. Differential Revision: https://phab.mercurial-scm.org/D1991

wireprotoserver: make abstractserverproto a proper abstract base class Plug in the abc module so we can have run-time validation of type conformance. Differential Revision: https://phab.mercurial-scm.org/D1990

wireprotoserver: make response handling attributes private The send* methods are specific to sshserver and aren't part of the common protocol interface. So rename them accordingly. The handlers dict is also specific to sshserver and is related to these methods. So give it the same treatment. Differential Revision: https://phab.mercurial-scm.org/D1989

wireprotoserver: make some instance attributes private sshserver attempts to conform to a well-defined interface. The instance attributes changed as part of this commit don't appear to be part of that interface. So prefix them with _ to mark them as private. Differential Revision: https://phab.mercurial-scm.org/D1988

wireprotoserver: remove sshserver.getarg() AFAICT the last consumer of this helper method was removed by d054cc5c7737 in 2010. Differential Revision: https://phab.mercurial-scm.org/D1987

wireprotoserver: remove lock references AFAICT sshserver.lock is unused. The last caller of it disappeared in 9f6e0e7ef828 ~18 months ago as part of removing code to support ancient wire protocol commands. Let's remove some dead code. Differential Revision: https://phab.mercurial-scm.org/D1986