Compute repository checksum by default

What does this MR do?

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• [-] Documentation created/updated
• [-] API support added
• [-] Tests added for this feature/bug
• Review
  • [-] Has been reviewed by UX
  • [-] Has been reviewed by Frontend
  • Has been reviewed by Backend
  • [-] Has been reviewed by Database
• [-] Conform by the merge request performance guides
• [-] Conform by the style guides
• Squashed related commits together
• [-] Internationalization required/considered
• [-] End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

1. gitaly#1146 (closed)
2. gitaly#1105 (closed)