- Add new temporary column id_convert_to_bigint to
  events table
- Add triggers to keep events.id_convert_to_bigint
  in sync with events.id
- Create batched background migration with job
  CopyColumnUsingBackgroundMigrationJob to backfill
  events.id_convert_to_bigint
- Add new tenmporary column event_id_convert_to_bigint to
  push_event_payloads table
- Add triggers to keep push_event_payloads.event_id_convert_to_bigint
  in sync with push_event_payloads.event_id
- Create batched background migration with job
  CopyColumnUsingBackgroundMigrationJob jobs to backfill
  push_event_payloads.event_id_convert_to_bigint