interfaces: convert `repository.peer` to a Protocol class...
interfaces: convert `repository.peer` to a Protocol class
This is similar to the transformation in
3a90a6fd710d for dirstate. However,
`ipeerbase` isn't referenced anywhere other than the `implementer` decorator on
this class. I suspect, based on the lack of `self` args on these classes prior
to c1674551c109, that zope enforced that interfaces and implementations are
separate entities. `Protocol` does not, so fold the former interface definition
into the class.
Per (seemingly undocumented) pytype desire, the `Protocol` subclass comes last
in the list.
