fix-1547-Bug-in-_partial_fit_and_predict_iterative-in-train_evaluator.py_ (#1550)

* Create PR

* Fix issue with incorrect splits and data

* Remove extraneous indexing

* Fill in missing points of X_data to self._loss

* Fix typevar

* Fix X data passed in to loss

* Fix indexing of X_fold for train evalutor

* Fix cv-iterative-fit successive halving example

Author: eddiebergman