Move optimizer libraries to extra requirements about hpobenchexperimentutils

[NeoChaos12]

Another alternative is to move each optimizer to its own module and import the modules only when needed.

[PhMueller]

Sounds good! Iike the second idea more. Is this okay for you? But to be honest I don't have a particular reason for this approach 😄

Then I would do it as soon as possible.

[PhMueller]

Commit 3be78ee includes the desired changes.

[NeoChaos12]

I think this would be necessary if you don't want to install and set up dragonfly just in order to avoid import errors. Likewise, I would prefer to avoid installing SMAC unless I actually need to use it.