* [Enhancement] Add PolyParamScheduler, PolyMomentum and PolyLR

* min_lr -> eta_min, refined docstr

* Fix pt1.5 unit tests.

* move to mmengine.testing

* [Feature]: Add parameter schedulers.

* update

* update

* update

* update

* add docstring to lr and momentum

* resolve comments

* tmp

* add scheduler unit test

* disable yapf

* add more test

* add more test

* not use torch test case

* solve comments

* update file

* add more unit tests

* resolve comments

* update cosine ut

* fix typo

* solve comments

* solve comments

* resolve comments