Clear up static resources of default Helper at deactivate

Static fields in the default helper class Helper are used to retain state created by its builtin operations such as flags, counters, trace streams etc. Rule scripts do not always clear out such rule state after a test or monitoring run.

Ideally, when all rules employing class Helper are uninstalled the deactivated lifecycle method of class Helper should clear all such resources, ensuring that any newly loaded rules do not see rule state belonging to a previous test run or monitoring session.

Implementation of this feature requires a prior fix to BYTEMAN-348.