* [Feature] Support EMA and SWA.

* add ema hook

* add avg model ut

* add more unit tests

* resolve comments

* fix warmup ema

* rename

* fix comments

* add assert

* fix typehint

* add comments

* [Fix]: Fix model_wrapper and add DistSamplerSeedHook as default hook.

* add comments

* add mmddp

* update

* update code

* update unittest

* fix comment