Use direct references for some configuration variables (#10798)

Instead of proxying through the magic getter of the RootConfig
object. This should be more performant (and is more explicit).

synapse/replication/tcp/client.py

@@ -73,7 +73,7 @@ class DirectTcpReplicationClientFactory(ReconnectingClientFactory):
     ):
         self.client_name = client_name
         self.command_handler = command_handler
-        self.server_name = hs.config.server_name
+        self.server_name = hs.config.server.server_name
         self.hs = hs
         self._clock = hs.get_clock()  # As self.clock is defined in super class