Check propagation of required branch names from within algorithms

It appears that tree branches needed by Observables used within algorithms may not be properly enabled. Likely this is because we currently only poll Observables/cuts used directly in the visitors and not, e.g., those wrapped by the TQAnalysisAlgorithm (relevant, e.g., for unfolding measurements).

This goes back to some oddities initially privately reported by @cbecot who shall hereby be tagged.