Make ReconstructedChargedParticles a subset collection of ReconstructedParticles

[simonge]

Is your feature request related to a problem? Please describe.
At the moment Low-Q2 tagger events are added to the CombinedTracks collection in tracking.cc, these are then unnecessarily passed through the PID algorithms and cluster matching I would like to be able to add them directly to the ReconstructedParticles collection at the end. This will make the code more efficient and allow PID to be approached differently (mostly just set to electrons). The Far-Forward detectors would also be better placed to use this separate pathway.

The one place the FF(/FB) tracks provide information required earlier in the tracking is in vertexing and t0

Describe the solution you'd like
Anything at the moment called a ReconstructedCharged***Particle could be renamed e.g. ReconstructedTracker***Particle to better reflect the status of the collection in the reconstruction chain. Collections of particles from the FF/FB detectors which can take a different reconstruction pathway and acquire their PID can the be added together in the ReconstructedParticles collection. Subset collections can then be made from the full ReconstructedParticles collection to reproduce the charged/neutral/other subset collections.

The consumption of ReconstructedChargedParticles in the current setup would not need to be changed.

It may be better if ReconstructedParticles itself was not a subset collection for easier follow on analysis.