Use LONGBLOB and TEXT for arbitary length rows

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

synapse/storage/schema/delta/15/appservice_txns.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/transactions.sql

...e/storage/schema/full_schemas/16/application_services.sql

synapse/storage/schema/full_schemas/16/event_signatures.sql

synapse/storage/schema/full_schemas/16/im.sql

synapse/storage/schema/full_schemas/16/keys.sql

synapse/storage/schema/full_schemas/16/push.sql

synapse/storage/schema/full_schemas/16/transactions.sql