Convert federation client to async/await. (#7975)

changelog.d/7975.misc

contrib/cmdclient/console.py

synapse/crypto/keyring.py

synapse/federation/federation_client.py

synapse/federation/sender/__init__.py

synapse/federation/transport/client.py

synapse/handlers/groups_local.py

synapse/http/matrixfederationclient.py

tests/crypto/test_keyring.py

tests/federation/test_complexity.py

tests/federation/test_federation_sender.py

tests/handlers/test_directory.py

tests/handlers/test_profile.py

tests/http/test_fedclient.py

tests/replication/test_federation_sender_shard.py

tests/rest/admin/test_admin.py

tests/rest/key/v2/test_remote_key_resource.py

tests/test_federation.py