* [Feature] Support torch ZeRORedundancyOptimizer

Co-authored-by: Junhwa Song <ethan9867@gmail.com>
Signed-off-by: Junhwa Song <ethan9867@gmail.com>
Signed-off-by: Hakjin Lee <nijkah@gmail.com>

* lint

* Fix saving optimizer state_dict

* Fix handling import error

* Add test case

* fix UT

* Revert "fix UT"

This reverts commit dd64538960ff7440c6020f533d43945ffc23f2d2.

* fix handling import in UT

* Fix saving zero checkpoint and delete redundant master_only

* lint

* test unittest

* Fix handling impor error

* Fix UT condition

* Edit docstrings

* Fix typo

* Skip redundant procudure in checkpoint hook

* fix typo again

* Update mmengine/optim/optimizer/zero_optimizer.py

Co-authored-by: Zaida Zhou <58739961+zhouzaida@users.noreply.github.com>

* Add api info

* lint

* Fix lint

* Handling AmpOptimWrapper case

* handling overlap_with_ddp

* Fix error

Signed-off-by: Junhwa Song <ethan9867@gmail.com>
Signed-off-by: Hakjin Lee <nijkah@gmail.com>
Co-authored-by: Junhwa Song <ethan9867@gmail.com>
Co-authored-by: Zaida Zhou <58739961+zhouzaida@users.noreply.github.com>