FastCaloSim integration as a Geant4 fast simulation engine
This adds a first implementation of FastCaloSim as a Geant4 fast simulation engine, running independent of ISF. For the Run-3 geometry, the fast simulation is triggered when particle reach one of the following volumes/envelopes 'CALO::CALO', 'LArMgr::LAr::Endcap::Cryostat::Cylinder::Mixed','LArMgr::LAr::Barrel::Cryostat::MotherVolume','LArMgr::ModeratorTube' The rationale behind this and more information is documented in https://indico.cern.ch/event/1168486/. The MR also adds a new ART test test_AtlasG4_FastCaloSim.sh in order to test the new configuration and a new STvsMT test test_AtlasG4_FastCaloSim_STvsMT.sh to check for differences with respect to AthenaMT. A CA configuration will be added in a later MR.