Into one unit test file

Update copyright for notest_dist_image_classification 

Make notest_dist_image_classification  consistent with distributed implementation in others. (#7899)

* Make this file consistent with others

* fixed style

* Add one_hot operator.

* Add more unit tests.

* Add distributed implementation for recommender system

* Addressing code review feedback

In notest_dist_label_semantic_roles.py, "emb" is matched with
"embedding_1.w_0", but they are two irrevalent vars.

Fixes: https://github.com/PaddlePaddle/Paddle/issues/7701

* remove pick dependency

* fix bug

* small fix

* modify executor.py for save and load

* clean code

* Add usage example

* refine executor run function

* fix bug

* refine executor code

* fix block bug

* fix comments

* fix bug

* fix pass num

Unify the recognize_digits