[ATR-20986] Add StoreGate key filtering in BJet monitoring
Works around a current known limitation in the TDT which can result in more "features" being returned than expected due to the presence of other chains which accept objects from earlier Steps.
Also adds a bit extra optional VERBOSE print out which was used to find this.
CC @enagy for change to Trigger/TrigMonitoring/TrigBjetMonitoring/src/TrigBjetMonitorAlgorithm.cxx