ISFTruthIncident / ISF_Fatras - Improve robustness + fix warnings

The changes in this merge request should finally fix the many warnings seen when running simulation using ISF_Fatras. There are two main sets of changes:

1. ISFTruthIncident: Add methods to properly update ISFParticles after the Truth Incident has been registered with the TruthSvc. The ISFTruthIncident::updateHepMCTruthParticle() method was changed to only update the ISF::TruthBinding of the ISFParticle in question. This is because a valid (GenParticle::)id value and hence a valid HepMcParticleLink can only be obtained after a new GenParticle has been added to the GenEvent - this occurs within the TruthSvc, not within the ISFTruthIncident. Instead ISFTruthIncident::updateParentAfterIncidentProperties() and ISFTruthIncident::updateChildParticleProperties() can be called to sync up the ISFParticle properties after the call to TruthSvc::registerTruthIncident(). These handle all cases except the case where the parent particle survives the interaction, but is not recorded to the GenEvent (for a follow-up MR).
2. Updates to ISF_Fatras classes (+ FastCaloSimV2Tool). All ISFParticles for secondaries created by Fatras should not have barcode/id/truthBinding/particleLink set initially. These should be set by the calls to TruthSvc::registerTruthIncident(), ISFTruthIncident::updateParentAfterIncidentProperties() and ISFTruthIncident::updateChildParticleProperties(). These calls should all be made before any particles are passed back to the ParticleBroker. No TruthBinding for secondaries should be set directly by the ISF_Fatras code. (NB For the special case of particles being returned to the ParticleBroker having not interacted, then the returned ISFParticle should have the same barcode/id/truthBinding/particleLink as the initial ISFParticle - this has to be set manually in the McMaterialEffectsUpdator code.

(Note to review shifters - it's probably best to review this with whitespace changes switched off. The ISF_Fatras classes need a larger clean-up, but that is beyond the scope of this merge request.)

Simulation/ISF/ISF_Fatras/ISF_FatrasToolsG4/src/G4ParticleDecayHelper.cxx

@@ -239,17 +239,23 @@ void iFatras::G4ParticleDecayHelper::handleDecayParticles(const ISF::ISFParticle
         decayProduct->setNextGeoID( particle.nextGeoID() );
       }//loop over all decay products
 
-      // register TruthIncident
-      ISF::ISFTruthIncident truth( const_cast<ISF::ISFParticle&>(particle),
-                                   decayProducts,
-                                   process,
-                                   particle.nextGeoID(),  // inherits from the parent
-                                   ISF::fKillsPrimary );
-      m_truthRecordSvc->registerTruthIncident( truth);
-      // At this point we need to update the properties of the
-      // ISFParticles produced in the interaction
-      truth.updateChildParticleProperties();
-
+      auto* truthBinding     = particle.getTruthBinding(); // TEMPORARY
+      HepMC::ConstGenParticlePtr hepTruthParticle = truthBinding ? truthBinding->getTruthParticle() : nullptr; // TEMPORARY
+      if (hepTruthParticle && hepTruthParticle->end_vertex()) { // TEMPORARY
+        ATH_MSG_WARNING("G4ParticleDecayHelper::handleDecayParticles(): Parent particle found with an end vertex attached.  This should not happen!");
+      }
+      else {
+        // register TruthIncident
+        ISF::ISFTruthIncident truth( const_cast<ISF::ISFParticle&>(particle),
+                                     decayProducts,
+                                     process,
+                                     particle.nextGeoID(),  // inherits from the parent
+                                     ISF::fKillsPrimary );
+        m_truthRecordSvc->registerTruthIncident( truth);
+        // At this point we need to update the properties of the
+        // ISFParticles produced in the interaction
+        truth.updateChildParticleProperties();
+      }
       // simulate the tracks of the daughter particles ------- run over decay products
       for (ISF::ISFParticle *decayProduct : decayProducts) {
         // feed it the particle broker with parent information