Push up the common run() and stop() methods from subclasses to ConcurrentGCThread, as well as declaration iof run_service() stop_service().
Reviewed-by: kbarrett, pliden
JEP-271. VM changes contributed by brutisso, test changes contributed by david.
Co-authored-by: David Lindholm <david.lindholm@oralce.com>
Reviewed-by: sjohanss, david, brutisso