Follow-up: Geo log cursor gap tracking improvements

What does this MR do?

It addresses the follow-up items from gitlab-org/gitlab-ee!6640:

• @ash.mckenzie started a discussion: (+3 comments)

  private removed?

• @ash.mckenzie started a discussion: (+2 comments)

  An example here of some values might assist?

• @stanhu commented on a discussion: (+2 comments)

  I think we still need Gitlab::Geo::LogHelpers? I think @ash.mckenzie was saying we don't need geo_logger. I'll revert your last commit and remove that method.

• @stanhu started a discussion:

  This could be an N+1 query. We might need to do this in batches.

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

Are there still N+1 queries?

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Conforms to the code review guidelines
  • Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
  • Has been reviewed by a Backend maintainer
  • Has been reviewed by a Database specialist
• EE specific content should be in the top level /ee folder
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• 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-and-qa manual pipeline job)

What are the relevant issue numbers?

Closes gitlab-org/gitlab-ee#7057.