Fix a few import path and init problems.

We have the initial support to import the model garden libraries as: import tensorflow_models as tfm tfm.nlp.XXX

Pypi package for 2.9.2 cut is: https://pypi.org/project/tf-models-official/2.9.2/

Note: how the symbols are exported is defined by: https://github.com/tensorflow/models/tree/master/tensorflow_models/ folder