Make work in both Maria and SQLite. Fix tests

synapse/app/homeserver.py

synapse/storage/__init__.py

synapse/storage/_base.py

synapse/storage/engines/__init__.py

synapse/storage/engines/maria.py

synapse/storage/engines/sqlite3.py

synapse/storage/keys.py

synapse/storage/registration.py

synapse/storage/schema/delta/12/v12.sql

synapse/storage/schema/delta/13/v13.sql

synapse/storage/schema/delta/14/v14.sql

synapse/storage/schema/full_schemas/11/event_edges.sql

synapse/storage/schema/full_schemas/11/event_signatures.sql

synapse/storage/schema/full_schemas/11/im.sql

synapse/storage/schema/full_schemas/11/keys.sql

synapse/storage/schema/full_schemas/11/media_repository.sql

synapse/storage/schema/full_schemas/11/presence.sql

synapse/storage/schema/full_schemas/11/profiles.sql

synapse/storage/schema/full_schemas/11/redactions.sql

synapse/storage/schema/full_schemas/11/room_aliases.sql