ISF_Fatras: use GenParticle::id() rather than barcodes in HepMcParticleLink constructors
This merge request is part of the preparation for migrating Athena away from using GenParticle barcodes (removed in HepMC3) as a unique identifier for truth particles to GenParticle::id() instead.
ISF_Fatras HitCreator tools updated to use id rather than barcode in HepMcParticleLink constructors.