Link master broken-incidents to related failure issues created automatically

Now that we have both master broken incidents created automatically and failure issues, we should link them together.

This will help with:

• issues being visible.
• Deciding on incidents and issues being flaky
• Possibly deciding severity and priority

Example of an incident with the linked issue

gitlab-org/quality/engineering-productivity/master-broken-incidents#3461 (closed)

Resources

• Issues links API https://www.rubydoc.info/gems/gitlab/Gitlab/Client/IssueLinks
• https://docs.gitlab.com/ee/api/issue_links.html#create-an-issue-link
• issue_notes https://www.rubydoc.info/gems/gitlab/Gitlab/Client/Notes#issue_notes-instance_method

Hints

We could use the /relate quick action instead of the API!