Backport changes in the application settings helper to CE

What does this MR do?

Backport changes in https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/4286

We now use repository_storage_options_for_select in Geo selective sync, so we need to be able to pass the list of enabled choices from more than one place.

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

Why was this MR needed?

Keep diff between CE and EE small.

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 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-qa manual pipeline job)

What are the relevant issue numbers?

Related to https://gitlab.com/gitlab-org/gitlab-ee/issues/4644