OnRC report

Currently, the information regarding an online revision cleanup execution is scattered across multiple log lines and partially available in the attributes of SegmentRevisionGarbageCollection MBean.
While useful for debugging, this is hard to grasp for users that need to understand the full process to be able to read it.

The idea would be to create a "report" with all the details of an execution and output it at the end - write to log, but also store it in the MBean, from where it can be consumed by monitoring and health checks.

In the MBean, this would replace the Last* attributes.
In the logs, this could replace all the intermediary logs (switch them to DEBUG).