* 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* outdated Env and note removed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 deps and prior comm

* grad comm fuse

* add deps for amp&global norm

* stage2 broadcast prior deps

* stage2 grad overlap

* stream_analyzer bugfix

* overlap enable

* dep op namescope

* depend support multiple inputs

* check finite deps

* stage2 param comm overlap

* Set kD2HStream

* grad comm hierarchical

* grad comm hierarchical

* new unitest
Co-authored-by: Nchenruibiao <chenruibiao@baidu.com>