Optuna v3.x.x no longer compatible with zombie trial cleaning

[RandomDefaultUser]

MALA implements a way to clean "zombie trials", i.e. trials which are not expected to finish anymore (e.g., because the original job broke). The API for this has changed from optuna v3 to v2, and this function no longer works. The regular MALA-optuna interface still works, but this particular part is currently not-functional. As it is important for extended, distributed hyperparameter optimization, I marked this as "critical".
Fixing this should not be too hard.

[timcallow]

[elcorto]

In Optuna 3.x the API has changed slightly:

set_trial_state(trial_id, state) -> set_trial_state_values(trial_id, state, values=None)