* [Fix] Convert SyncBN to BN when training on DP.
* Modify SyncBN2BN.
* Add SyncBN2BN unit test.
* Resolve some comments.
* use mmcv official revert_sync_batchnorm
* Remove local syncbn2bn unit tests.
* Update mmcv version.
* Fix bugs of gather model tools.
* Modify warnings.
* Modify docker mmcv version.
* Update mmcv version table.
* Add save_best option in eval_hook.
* Update meta to fix best model can not test bug
* refactor with _do_evaluate
* remove redundent
* add meta
Co-authored-by: Jiarui XU <xvjiarui0826@gmail.com>