We have shipped backfilling migrations to .com. This issue is about releasing those migrations, so that also self-hosted installations execute those migrations. ### Tasks * [x] %"13.12" Enable `execute_batched_migrations_on_schedule` feature flag by default (https://gitlab.com/gitlab-org/gitlab/-/merge_requests/61316) * [x] %"13.12" Enable `optimize_batched_migrations` feature flag by default (https://gitlab.com/gitlab-org/gitlab/-/merge_requests/61317) * [x] %"14.0" Start backfilling PK conversion for these tables (https://gitlab.com/gitlab-org/gitlab/-/merge_requests/61321): * [x] events * [x] push_event_payloads * [x] ci_job_artifacts * [x] ci_sources_pipelines * [x] ci_build_needs * [x] ci_builds * [x] ci_builds_runner_session * [x] ci_build_trace_chunks