Define and bootstrap a process to collect & analyze false positives in Jenkins test suite runs

We’ve enabled notifications for these runs a bit more than a month ago. Since then, there have been lots of false positives. Presumably because there are so many (and then bogus notifications are the rule more than the exception), nobody told the CI team about it. And nobody on the CI team, who received such notifications as well, dealt with it either. So in the end, until today, fragile tests were not flagged as such. This shows that we need a formal process to go on catching false positives, and to flag scenarios as fragile.

Parent Task: #5288 (closed)

Original created by @intrigeri on 10993 (Redmine)