CE to EE: refactor projects finder init collection ee

What does this MR do?

EE MR for gitlab-org/gitlab-ce!12135

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

Why was this MR needed?

This change from CE is causing EE specs to fail. This failure is blocking for %9.3 RC6, see gitlab-org/gitlab-ee!2195.

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
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

gitlab-org/gitlab-ce!12135