* limit time and memory
* separate tests
* lrl1 can't be limited by limit_resource
* free memory when possible
* passthrough=False when ensemble fails;
retrain when trained_estimator is None
* use callback to for resource limit
* handle lower version of xgb with no callback
* free mem ratio
* reduce verbosity
* retrain_final when max_iter==1
* remove trained_estimator from result
* model_history
* wheel
* retrain time as best_config_train_time
* ci: libomp version for xgboost on macos
* limit_resource not working in windows
* test pickle load
* mute forecaster
* notebook update
* check hard
* preventive callback
* add use_ray
