MEDIUM: sock_unix: use per-family addrcmp function

MEDIUM: sock_unix: use per-family addrcmp function

Thanks to previous commit, we may now use dedicated addrcmp functions for
each UNIX address family. This allows to simplify sock_unix_addrcmp()
function and avoid useless checks in order to try to guess the socket
type.

In this patch we implement sock_abns_addrcmp() and sock_abnsz_addrcmp()
functions, which are respectively used for ABNS and ABNSZ custom families

sock_unix_addrcmp() now only holds regular UNIX socket comparing logic.