move common code to abstract gia

[viktorvaladi]

to move .run_attack(), inverting needs to move to the generator structure (which it should to allow for early stopping in hyperparameter tuning with optuna) the rest should be the same between the two current attacks. The code could for now be in abstract GIA, but if we find that other attacks that does not share this loop we should consider moving it somewhere else.

Same goes for the function "reconstruction_costs", can also be moved to abstract gia for now.