* [dygraph]unify _non_static_mode() in_dygraph_mode() and in_dynamic_mode()

* [dygraph]unify _non_static_mode() in_dygraph_mode() and in_dynamic_mode()

* [dygraph]unify _non_static_mode() in_dygraph_mode() and in_dynamic_mode()

* [dygraph]unify _non_static_mode() in_dygraph_mode() and in_dynamic_mode()

* [dygraph]unify _non_static_mode() in_dygraph_mode() and in_dynamic_mode()

* [dygraph]unify _non_static_mode() in_dygraph_mode() and in_dynamic_mode()

* fixed cyclic reference that caused patial import

* fixed bad change

* fix bad import

* fix bad import

* fix bad import

* fix ut failed caused by change in_dynamic_mode

* fix ut failed caused by change in_dynamic_mode

* fixed usage of in_dynamic_mode() or in_dygraph_mode()

* revert python3 to python in .pre-commit-config.yaml

* fix merge conflicts

* isort all files

* revert conflicting files

* revert conflicting files

* revert conflicting files

* clear fluid api: warpctc, nce, identity_loss

* fix test_layers.py __init__.py

* fix loss.py

* change __init__.py and api calling method

* fix nce

* fix nce

* fix fluid.data

* delete warpctc api document

* fix loss.py

* fix ctc_loss

* fix test_warpctc_op.py

* fix test_layers.py

* fix some bug

* fix conflict

* fix ci bug

* Empty Commit test=allcase

* fix ci bug