CaloTrackingGeometry : Put the common (1500+ lines) implementation in one place, avoid duplication

We have an "issue" that leads to code duplication.

Every GeometryBuilder implementation is duplicated . Or so we think/hope as otherwise we do not use the same in reco and simulation ...

Once for the Conditions and once for the Service.

In reality we would like to get rid of the Service but this might not be possible/practical for simulation.

In this MR

• We create an Impl clas.
• We move all the common things to it .
• Note that is NOT new code but copy paste of the "common" code
• So it has the same "issues", but now in one place not two (so potentially easer to solve in the future?)
• The 2 derived ones differ on how one "gets" the EventContext
• So we end up with a single 1500 lines impl, rather than 2 ...

This follows some discussion with @jchapman, do not know how close is to what he had in mind. Let me ping also @tsulaia

Now if this works we can try to do something similar in the other builders.