* remove dygraph.parallel.ParallelEnv

* logger.py error: AttributeError: module 'paddle' has no attribute 'distributed'

* move the implenmentation to the root folder

* logger.py import ParallelEnv from paddle.parallel to avoid circular import

* add the comment of why import ParallelEnv from paddle.parallel in logger.py and remove the api interface in the paddle/parallel.py

* outdated Env and note removed

* decouple the logger.py and ParallelEnv

* remove another ref of parallel in init.py

* remove custom op eager guard tests

* rm custom_runtime eager guard tests

* rm xccl eager tests

* modify

* modify

* set grad retain for custom_relu test

* retain grad for custom relu op

* modify custom_relu test

* add isort config

* isort all files

* refactor: update pg custom

* fix: use new api in ut

* fix: typo

* revert: recover legacy apis

* fix: add GetDeviceContext

* update config

* re-blacken python code

* temporarily disable date and diff_py_file

* skip a format

* [CodeStyle] remove all future import

* revert test_error.py

* restore future import in example code

* [CustomDevice] add process_group_xccl ut

* update

* use yapf to format all python file

* yapf exclude two unittests file for they rely on writing and reading file, and format will break them

* disable diff_py_file because too many diff files cause command following failed

* add pg_hccl

* add processgroup_nccl