Port rest/v1 to async/await

synapse/app/synchrotron.py

synapse/rest/client/v1/directory.py

synapse/rest/client/v1/events.py

synapse/rest/client/v1/initial_sync.py

synapse/rest/client/v1/login.py

synapse/rest/client/v1/logout.py

synapse/rest/client/v1/presence.py

synapse/rest/client/v1/profile.py

synapse/rest/client/v1/push_rule.py

synapse/rest/client/v1/pusher.py

synapse/rest/client/v1/voip.py