Resolve "Move EE differences for `app/views/admin/users/show.html.haml`"

What does this MR do?

• Moves EE-specific business to the ee/ folder
• Renames some template files because what was user_detail_note was actually used in the user listing, therefore:
  • user_detail_note was renamed to user_listing_note
  • the new EE-only template used in the user detail view has been named as user_detail_note 🎉

What are the relevant issue numbers?

#6099 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• ~~Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.~~
• Security reports checked/validated by reviewer

Closes #6099 (closed)