Add Pruning

[SammyRamone]

In cases where we do multiple repetitions or increasingly difficult ones, it would be nice to use the optuna pruning, to improve the time needed for optimization

[SammyRamone]

After thinking about it I think, its not usable for the walking. Since the objective get increasingly difficult, the score does not improve over time. Pruning in cases where the robot fails to walk with the given velocity, we terminate early anyway.
It would maybe still make sense for Dynup where there is just the repetition of one same trial
more detaisl about it https://optuna.readthedocs.io/en/stable/tutorial/10_key_features/003_efficient_optimization_algorithms.html#pruning-algorithms