* [Refactor] Refactor the rest data transforms and fix some docstring.
* Use `mmengine` instead of `mmcv`
* Refactor KFold dataset tools
* Fix docstring according to comments
* Refactor unit tests folder structure.
* Remove label smooth and Vit test in `test_classifiers.py`
* Rename test_utils in dataset to test_dataset_utils
* Split test_models/test_utils/test_utils.py to multiple sub files.
* Add unit tests of classifiers and heads
* Use patch context manager.
* Add unit test of `is_tracing`, and add warning in `is_tracing` if torch
verison is smaller than 1.6.0
mzr1996