Create tool to monitor clustering thread pool usage

Scheduled executors and thread pools are used widely in JGroups and Infinispan for asynchronously executing tasks. When thread pools are not adequately sized to the load they are subjected to, this can lead to performance problems.

It would be helpful if we could see thread pool usage as a function of elapse time during performance runs, in order to diagnose potential thread pool issues.

This task will provide a Byteman-based tool to monitor threadpool usage and allow a report to be attached to SmartFrog test jobs.