* [Enhance] Optimize parameter updating speed in AveragedModel.

* add docstring

* [Fix] Fix some bugs in hooks and runner.

* fix markdown

* fix latex formula

* resolve comments

* [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