Update TrkPID to use track-based observables

[michaelmackenzie]

This update includes:

• Moving to flat electron and muon samples for training inputs
• Replacing E - P with E/P
• Removing R(cluster) and track p dot cluster x observables
• Adding track p(chi^2) and tracker hit dt/dz over the expected slope from the track fit

To add the tracker hit dt/dz, I'm adding a branch to the EventNtuple tree for each track, as it's not yet in EventNtuple. I think this observable should ideally be added to the KalSeed data product and then naturally added to the TrkInfo struct in EventNtuple.

As the ONNX features aren't yet available in pyenv rootana the model has not been exported to ONNX or added to Offline processing yet.

Input features and output predictions: