Printing Multi-statistics to hyperopt json files

Created by: Cmurilochem

This would be an extension of #1726 and a direct application of the newly implemented HyperLoss class.

Despite opting for a specific statistics whose values are used as metrics for the hyperoptimization, it would be nice to also be able to print all statistics, i.e., average, best_worst and std, for hyper_loss (and possibly for validation_loss and experimetal_loss) in the json file. For this we would need to adapt and instantiate HyperLoss several times.