test alternatives to optuna, in particular for random sampling

[klieret]

The fact that optuna cannot do conditional categorical distributions is really annoying. Let's find some other framework that can?

Also if we switch to purely random sampling, there are probably easy and fully flexible solutions out there.

[klieret]

Hyperopt: Supports restore; easy syntax, but cannot do the suggest_default trick that we're currently doing.

https://docs.ray.io/en/latest/tune/examples/includes/hyperopt_conditional_search_space_example.html