QA: Fix waiting for Geo replication tests when replication is slow

What does this MR do?

I attempted to run Geo QA specs against staging, and all 3 specs failed because the GSTG DB was over a minute behind, and we haven't accounted for that possibility. This MR ensures that we wait properly for slow DB replication.

And it allows you to increase the replication timeouts with environment variables if needed.

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?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by Backend
• EE specific content should be in the top level /ee folder
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered
• If paid feature, have we considered GitLab.com plan and how it works for groups and is there a design for promoting it to users who aren't on the correct plan
• End-to-end tests pass (package-qa manual pipeline job)

What are the relevant issue numbers?

Related gitlab-com/migration#330 (closed)