* 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>

* mmcv eval hook

* mmcv evalhook compatible

* add warnings

* inherit from base class

* fix unitest

* adapt to mmcv 1.3.1

* fixed unittest

* set by_epoch=False

* fixed efficient test

* update docstring

Co-authored-by: Jiarui XU <xvjiarui0826@gmail.com>

* Add runner_type option

* pre-commit

* Fix max_iters

* Add by_epoch to EvalHook

* Add test_eval_hook for epoch runner

* Remove runner-type arg from tools/train

* Add missing every_n_iters check for epoch mode

* Bump mmcv min version

* Use build_runner

* Use interval in tests

* Update test_eval_hook.py

* Use every_n_epochs instead of every_n_iters. Update DistEvalHook

* Add test_dist_eval_hook_epoch

* Fix tests

* Add DeprecationWarning

* Update docs

* Replace DeprecationWarning with UserWarning