Hide clone panel and file list when user is only a guest (with review comments addressed)

What does this MR do?

This MR is based on https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10562

In fact, I only addressed review comments. The origin commit of @jameshclrk is preserved

The motivation behind this MR is that I already fixed the issue locally then I noticed that the MR already exists and looks like abandoned. The fix is pretty important.

@adamniedzielski I addressed all your comments here. Please take a look once again.

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

Why was this MR needed?

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• 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 #30432 (closed)

Closes #3142 (closed)

Closes #17489 (closed)