Adding TruthPileupEvents to variables stored in DAOD_PHYSVAL
Only TruthPileupParticles
were saved so far in DAOD_PHYSVAL, while the InDet PhysVal monitoring also relies on the TruthPileupEvents
to monitor the pile-up content in the full truth config. The collection is therefore added here. Solves the following warning observed in the full truth Upgrade campaigns ART test https://gitlab.cern.ch/atlas/athena/-/blob/master/Tools/CampaignsARTTests/share/test_digi_reco_inTimeTruth_mu1.sh
03:22:40 WARNING Truth Strategy for InDetPhysValMonitoring set to All but TruthPileupEvents are missing in the input; resetting to HardScatter only