* fix bug of not save-best in iteration-based training

* revise the unit test

* [Feat] Support save best ckpt

* reformat code

* rename function and reformat code

* fix logging info

* support resume from ceph

* move func and refine

* delete symlink

* fix unittest

* perserve _allow_symlink and symlink

* 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