Resolve "Close GitLab issue on Recovery alerts from Prometheus"

What does this MR do?

This requires !18046 (merged) to be merged. The base is currently set to that branch so that these MR changes are easy to review.

This MR adds functionality to automatically close an Issue that was opened by a Prometheus alert. When we receive a payload with the resolved status, we look for the Alert using the payload_key.

If an alert is found then we close it while leaving a system note which tells the user that the issue was closed because we received a resolved alert from Prometheus.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Closes #13401 (closed)