Added layer_test in addons and refactoring the code

[ashutosh1919]

We need to modify code in many files to resolve issue #1567 .
This PR adds layer_test in testing_utils of addons.
@gabrieldemarmiesse - I have removed all codes in the function corresponding to model checking and set|get_weights(). Currently, tests will fail because the method doesn't return anything (previously it was returning something like actual_output which was part of Sequential API tests part.). Please review the code and guide me to the right direction.

[gabrieldemarmiesse]

• We don't need a model for the tests but we still need to do a foward pass to ensure that no exception is raised. To get the output values just do output_tensor = layer(input_tensor).numpy(). So we can still return the result without using a keras model.

• Another thing to check is that the layer output the same numbers after being serialized and deserialized.

[ashutosh1919]

@gabrieldemarmiesse , I have added codes as per you comment. But still many tests fails. Tests fails because of lib NotFoundError. Please can you take a look and give me a hint?

[gabrieldemarmiesse]

You don't need to use a keras model here. Can you try that and see if the NotFoundError is still there? Thanks a lot

[ashutosh1919]

cc @bhack

[seanpmorgan]

Thank you for your contribution. We sincerely apologize for any delay in reviewing, but TensorFlow Addons is transitioning to a minimal maintenance and release mode. New features will not be added to this repository. For more information, please see our public messaging on this decision:
TensorFlow Addons Wind Down

Please consider sending feature requests / contributions to other repositories in the TF community with a similar charters to TFA:
Keras
Keras-CV
Keras-NLP