Merge pull request #6484 from matrix-org/erikj/port_sync_handler

changelog.d/6484.misc

synapse/handlers/events.py

synapse/handlers/sync.py

synapse/handlers/typing.py

synapse/notifier.py

synapse/storage/data_stores/main/account_data.py

synapse/storage/data_stores/main/group_server.py

synapse/util/metrics.py

tests/handlers/test_sync.py

tests/handlers/test_typing.py

tests/rest/client/v1/test_typing.py

tests/unittest.py