This had been partially implemented, but never completed (TP converters existed for
LUCID_SimHit, but not the hit collection itself). Will make similar changes in the 21.X branches (taking care to write out
LUCID_SimHitCollection_p1 from 21.0).
Doing this now as the HepMC3 migration in master would otherwise prevent reading LUCID hits writtrn by older releases.