Move all FF for archived search to user actors

What does this MR do and why?

Noticed during roll out of search_projects_hide_archived in #413821 (closed)

The backend feature flags are not gated to an actor. The frontend code (for projects) and eventually for the other flagged scopes sends a user actor.

This MR:

• updates the flag check on the backend to add a current_user actor
• fixes rubocop todos for lib/gitlab/search_results.rb (1 todo was not fixable easily so I left it)

Screenshots or screen recordings

N/A

How to set up and validate locally

FF_NAME	SCOPE	TAB	BASIC GROUP SEARCH?
:search_commits_hide_archived_projects	commits	Commits
:search_merge_requests_hide_archived_projects	merge_requests	Merge Requests	✅
:search_notes_hide_archived_projects	notes	Comments
:search_projects_hide_archived	projects	Projects	✅

For each Feature Flag, verify using the steps below.

1. Archive one project in a group (or use an existing archived project)
2. Enable elasticsearch in gdk (if not already enabled)
   1. index everything using gitlab:elastic:index rake task
   2. enable search with advanced search
3. Find a value to search for in the scope
4. In rails console fully disable then enable FF_NAME for one user

   Feature.disable(:FF_NAME)
   Feature.enable(:FF_NAME, User.first)

5. Search for SCOPE in that group example: http://gdk.test:3000/search?scope=SCOPE&search=aut&group_id=46
6. Verify results are not returned from the archived project
7. Search for SCOPE in that group, but first add &include_archived=true onto the end of the URL example: http://gdk.test:3000/search?scope=SCOPE&search=aut&group_id=46&include_archived=true
8. Verify results are returned from the archived project
9. Repeat the steps above for Basic Search if supported. To force basic search add &basic_search=true to the URL or disable Search with Advanced Search from the Admin Settings

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.