Restore sub-slot debug information in event of stall

The dumpSchedulerState() method does not create output for sub-slots. The ability does exist, but was removed:

https://gitlab.cern.ch/gaudi/Gaudi/blob/master/GaudiHive/src/AvalancheSchedulerSvc.cpp#L863

Could it be added back on an optional or configurable basis? It would be very helpful for debugging stalls - perhaps just add a boolean argument for when dumpSchedulerState() is called from eventFailed()?

Alternatively a python-configurable option for the scheduler?

Regards, Ben