mlr3mbo 0.2.2

• refactor: compatibility with upcoming paradox upgrade.
• feat: OptimizerMbo and TunerMbo now update the Surrogate a final time after the optimization process finished to
  ensure that the Surrogate correctly reflects the state of being trained on all data seen during optimization.
• fix: AcqFunction domain construction now respects Surrogate cols_x field.
• feat: support more than one candidate point as a result of acquisition function optimization even for
  non-batch acquisition functions.
• feat: added default_gp and default_rf helpers that allow for construction of a default
  Gaussian Process and random forest as for example used within default_surrogate.
• refactor: changed Gaussian Process and random forest defaults (in default_gp and default_rf and therefore also in
  default_surrogate). Gaussian Process now uses a "matern5_2" kernel. Random forest now uses 100 trees.
  The number of trees used in the fallback random forest was reduced to 10.