- units from properties specified in ddsim_steer.py
   already are in G4units, so no conversion needed

Allow users to add track user information to G4 tracks, which then moves to Geant4Particle for saving

If excited state is already known we get it via FindIon. Otherwise we use GetIon to create zero-state ions and print warnings for lvl>0

If we do not already store particles that become important'ish later we get a fatal error because the equilavent finding might not be able to find this particle

This logic only incurs a runtime overhead of two if checks if no particles are ever suspended.
Store non-primary particles that are suspended in a different map to pick their initial information up later again.

ParticleHandler: account for modified stacking actions, were tracking of a particle could be paused and later restarted.

Pick up the particle information that we have stored and go on from there

Add track momentum to the MonteCarloContribution of Geant4Hit structures. See issue https://github.com/AIDASoft/DD4hep/issues/1037

Revert "Allow to set MeanExcEnergy, MeanEnergyPerIonPair and BirksConstant in G4Materials ionisation parameters"

This reverts commit 990be5d0.

Allow to set MeanExcEnergy, MeanEnergyPerIonPair and BirksConstant in G4Materials ionisation parameters