Send alert when benchmark runners are down

This is useful. The status of benchmark runners must currently be checked manually. They go down from time to time and when they do, results are not being uploaded. We must rectify the issue quickly, and an alert will help us to do this.

There is a system for sending out alerts to the people responsible. It was never merged and lives as a code review.
https://codereview.qt-project.org/c/qt/qtqa/+/603846

An instance of the alert tool is running on the graphics team Jenkins server.
https://graphicsteamjenkins.ci.qt.io/computer/nightly%5Fbots/

The Jenkins workspace.

/opt/jenkins/workspace/

This tool should be used to send out alerts.