Don’t create comment on JIRA if link already exists

What does this MR do?

When a JIRA issue is mentioned on a merge request or commit a link and comment is created on the JIRA issue. When title or description changes jira_service only updates the link (so that the title of that link is up to date) but does not create a new comment.

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

Why was this MR needed?

When we had an MR or a commit with JIRA issue link in the description / title and the title was changed or the description was changed by a new user a new link and comment were created. That is not expected behaviour. We don't want a new comment and link for every change.

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 #25373 (closed)