Return the last coverage in trace stream

What does this MR do?

This MR fixes the coverage issue raised at https://gitlab.com/gitlab-org/gitlab-ce/issues/31556. Currently, the first coverage appears in the trace will be considered as the coverage. Since general total scores will likely appear at the last part of logs, coverage extraction should be targeting the last matched part.

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

Need to be checked by @godfat

Why was this MR needed?

Because #31556 (closed) labeled as regression

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 #31556 (closed)