Pass an Interactor to new_connection().

Thanks to the previous commit, this new parameter can replace two of
the existing ones: instead of passing a LogPolicy and a Seat, we now
pass just an Interactor, from which any proxy implementation can
extract the LogPolicy and the Seat anyway if they need it.

otherbackends/supdup.c

@@ -759,7 +759,7 @@ static char *supdup_init(const BackendVtable *x, Seat *seat,
      */
     supdup->s = new_connection(addr, *realhost, port, false, true,
                                nodelay, keepalive, &supdup->plug, supdup->conf,
-                               log_get_policy(logctx), &supdup->seat);
+                               &supdup->interactor);
     if ((err = sk_socket_error(supdup->s)) != NULL)
         return dupstr(err);