decorate electrons and photons in PHYSLITE with E_mva_only
This is needed to give the correct input energy to the columnar EgammaCalibrationAndSmearingTool. It should also allow to run solely the smearing part of the tool in regular event-wise jobs.
In my test this was 44 bytes/event for PHYSLITE. So that's notable, but it is also part of the long-term plans for PHYSLITE. Long-term we will be able to drop the variables that are only needed for the calibration, as we will be able to skip calibation on PHYSLITE.
Not sure if this is the place that the e-gamma experts want this to be written out, so they should feel free to suggest a different place or fix this in a followup MR.