Backup/restore validation for OpenBao on GitLab CNH

Summary

Validate backup and restore procedures for OpenBao in Cloud Native Hybrid (CNH) environments.

Validation Steps

1. Backup OpenBao database
2. Restore OpenBao database
3. Verify Secrets Manager functionality after restore

Further Details

What: Test backup and restore of the OpenBao database in a 3k CNH environment, ensuring that secrets can be recovered after a restore operation.

Why it's separate: This validation is blocked by the decision on whether OpenBao should use the main GitLab Rails database by default, which is debated in #582640. Once that's resolved, we can validate the backup/restore procedures.