relation_cost is not included in the calculation of levelized_cost

[behnam-zakeri]

levelized_cost is used to calculate the penalty for the activation of soft constraints in the model. While the equation calculating levelized_cost should include all cost related parameters for technologies (see message_ix/model/MESSAGE/scaling_investment_costs.gms), it omits relation_cost. This can underestimate the penalty for those technologies that have cost associated to their capacity or activity, represented via relation_cost.