WIP: Add index of uploaded files within discussion to top of issue page

What does this MR do?

Works toward closing Issue #19562 (moved) by adding a list of uploaded files within the issue discussion to the top of the page.

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

This is my first merge request for GitLab. If it does not match the community code style guidelines or if there is something else that I may have glossed over, please let me know.

Why was this MR needed?

Was requested by @jschatz1 as part of an interview process.

What are the relevant issue numbers?

Issue #19562 (moved)

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together