tfdbg + tflearn: replace deprecated classes and methods in example & docs
tfdbg + tflearn: replace deprecated classes and methods in example & docs

* `tf.contrib.learn.Experiment` is deprecated. Remove it from debug_tflearn_iris.py.
* Use `tf.estimator.DNNClassifier`, instead of the older one from `tf.contrib.learn`.
* Use `train()`, instead of `fit()` of Estimators.
* `Estimator.predict()` supports hooks. Add example lines for that.

PiperOrigin-RevId: 195301913

tensorflow/docs-l10n,tensorflow/docs,tensorflow/docs,tensorflow/docs