[EE] Hashed Storage Attachments migration path

What does this MR do?

Fix conflicts for EE, from: gitlab-org/gitlab-ce!15352

Adds specific Geo code to handle the attachments migration

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

Why was this MR needed?

There was a conflict when merging CE to EE here: gitlab-org/gitlab-ce!15352 also the additional code in the merge request added need to have additional Geo event to migrate attachments folder in a secondary Geo node.

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
• 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

What are the relevant issue numbers?

Related to gitlab-org/gitlab-ee#3674