[RM-8011] [api] From AbstractOutput to COperatorResultStore

Created on 2023-04-07 12:57:34 by Ali Allaoui. % Done: 0

Between stages there is implicitly a communication through COperatorResultStore (e.g. between redshift_solver and linemeas_solver, or between N redshift_solvers and classification_solver). This communication could be made explicitly in the API if there was an equivalence between COperatorResultStore and AbstractOutput, but there only exists a conversion from COperatorResultStore to AbstractOutput and not the opposite, which could be quite complicated to implement. It's a problem because we need this to consider the stages independently in order to have a real modular pipeline that could use existing outputs as input (as we do with linemeas, but not in a normalized way)