Decoration of auxiliary quantities within jFEX Simulation

This MR slightly refactors parts of the jFEX simulation to allow for decorating jFEX TOBs with auxiliary quantities from within simulation. As various (intermediate) quantities are not part of the readout format they can only be investigated and potentially monitored by re-deriving them in software (i.e. the jFEX simulation). The latter is running anyways as part of various monitoring jobs to have, e.g., hardware/simulation comparisons available online.

As a first of such intermediate quantities this MR adds a decoration for the jJet seedET