See if kaon properties can be configured at runtime

[EinarElen]

One of the changes in https://github.com/LDMX-Software/geant4/tree/LDMX.upKaons_mod which would be useful to be able to make use of even without the kaon enhancement features of that branch is the changes to the decay modes and lifetimes of the charged kaons (Geant4/geant4@25228b8). If it is straight-forward to implement this kind of customization as a part of LDMX-sw rather than direct changes to Geant4, this could make it easier to do other studies with challenging kaon events.

I think this actually should be quite straight-forward to do, you should be able to access and configuring the decay table when constructing the physics.

[tomeichlersmith]

@EinarElen did some more excellent work diving into the Geant4 details and this is now patched by #110