- BatchedMigration model starts to use state_machine
- BatchedMigration has a new column (starts_at). When we
  perform the event execute, the system updates the
  starts_at with the current time.
- BatchedMigrationRunner stops the migration when a certain
  number of failed jobs is achieved

Changelog: added

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/355975