Add Geo attachment replication QA spec

What does this MR do?

Adds a QA spec to test Geo attachment replication.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Review
  • Has been reviewed by Backend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

Closes gitlab-qa#128 (closed)