Update ISF_Fatras Hit Creators to use HepMcParticleLink-based sim hit constructors
The main changes here are as follows:
- switch to using HepMcParticleLink-based constuctors for sim hits (as used in the Geant4 sensitive detector implementations)
- use Emplace to create the new sim hits directly in the sim hit containers
The other changes are mostly making a few variables const.
Edited by John Derek Chapman