Right now cross_val_score is a wrapper for cross_validate, but cross_val_predict has its own implementation.

We could make it also a wrapper around cross_validate, but for that to happen, we need to make cross_validate also return predictions. For that, we would also need to be able to pass y_pred, y_true to scorers instead of passing the estimator, which would also remove the need to cache in _MultimetricScorer and make things quite a bit cleaner.

cc @glemaitre

xref: #26896 (review)