Restructure core Digitization packages
Simulation/Digitization -> Simulation/Digitization/DigitizationConfig
Simulation/G4Utilities/MCTruthSimAlgs -> Simulation/Digitization/MCTruthSimAlgs
Perhaps also move the following in a follow-up MR?
Control/PileUpComps -> Simulation/Digitization/PileUpComps
Control/PileUpTools -> Simulation/Digitization/PileUpTools
Edited by John Derek Chapman