* change CheckPointHook before_run to before train

* using tmp_path in each checkpointhook test case

* [Refactor] Add batch_idx to hook input.

* update

* [Feature]: Add dist semantics in checkpoint hook

* [Fix]: Delete sync buffer in checkpoint hook

* [Feature]: Add checkpoint hook

* [Fix]: Fix lint

* [Fix]: Delete redundant optional and give an example to our_dir

* [Feature]: Add test the last_ckpt in UT

* [Fix]: Fix docstring problem

* [Fix]: Add patch to UT

* [Feature]: Add Test case for by epoch