- Add optional `?mode=fast|immediate` to `/terminate`, `fast` is
default. Immediate avoids waiting 30
seconds before returning from `terminate`.
- Add `TerminateMode` to `ComputeStatus::TerminationPending`
- Use `/terminate?mode=immediate` in `neon_local` instead of `pg_ctl
stop` for `test_replica_promotes`.
- Change `test_replica_promotes` to check returned LSN
- Annotate `finish_sync_safekeepers` as `noreturn`.
https://github.com/neondatabase/cloud/issues/29807