Expose CI/CD status API endpoints with Gitlab::Ci::Status facility on pipeline, job and merge request for favicon

What does this MR do?

Follow-up for !8878 (closed) , especially focusing on Backend task.

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

Why was this MR needed?

Because

One approach is a using legacy statuses and the other is the new using new detailed statuses facility

Here is the original comment

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated(No need)
• API support added(No need)
• 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?

• !8878 (closed)