Refactor wiki_blobs and epics search nav and specs

What does this MR do and why?

Found while working on !142833 (merged)

• Refactor code that is EE so it's separated properly into the /ee path for wiki_blobs search scope
• Refactor how checks are written for epics search scope
• Refactor specs to add missing checks (for group searches) and hopefully increase readability

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

How to set up and validate locally

Presetup

1. setup gdk for advanced search and index the entire instance

This change is about whether the navigation option shows up in the left sidebar. So there is no need to actually do searches per-se to validate this

Advanced search enabled

bundle exec rake gitlab:elastic:enable_search_with_elasticsearch

1. global search page http://gdk.test:3000/search

• wikis are visible
• epics are visible

2. group search page http://gdk.test:3000/search?group_id=33

• wikis are visible
• epics are visible

3. project search page

• wikis are visible
• epics are NOT visible

Advanced search disabled

bundle exec rake gitlab:elastic:disable_search_with_elasticsearch

1. global search page http://gdk.test:3000/search

• wiki are NOT visible
• epics are NOT visible

2. group search page http://gdk.test:3000/search?group_id=33

• wiki are NOT visible
• epics are visible

3. project search page

• wiki are visible
• epics are NOT visible