Allow admins and auditors to perform global searches with Elasticsearch

What does this MR do?

Makes the elasticsearch code path for global searches work for admins and auditors

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

This needs refactoring before it's acceptable to me, neither mind a reviewer!

Why was this MR needed?

Feature parity with ordinary search functionality

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• 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?

Closes #1646 (closed)