* Fix bug of reduce_sum op. When input.numel() > INT32_MAX, its result
is wrong.

* Remove climits.

* Clean fluid API in paddle/distributed and paddle/fleetx folders.
Include following files:
python/paddle/distributed/__init__.py
python/paddle/distributed/collective.py
python/paddle/distributed/fleet/utils/fs.py
python/paddle/distributed/fleet/utils/hybrid_parallel_inference.py
python/paddle/distributed/fleet/utils/hybrid_parallel_util.py
python/paddle/distributed/fleet/utils/internal_storage.py
python/paddle/distributed/launch/context/device.py
python/paddle/distributed/parallel.py
python/paddle/distributed/parallel_with_gloo.py
python/paddle/distributed/spawn.py
python/paddle/framework/__init__.py
To be mentioned, 'paddle.fluid.dygraph.parallel.ParallelEnv'
 and 'fluid.framework.core' keeps unchanged in those files.
ParallelEnv is used by paddle.fluid.dygraph.parallel.DataParallel.
However, APIs in paddle.fluid.dygraph.parallel can't be
migrated to paddle.distributed, as there exists cyclic import
dependencies in modules like paddle.static, paddle.tensor. And
'fluid.framework.core' will be changed to import framework.core
after fluid.core is transmitted.

* Change TODO authors.

* isort all files

* revert conflicting files

* revert conflicting files

* revert conflicting files

* update config

* re-blacken python code

* temporarily disable date and diff_py_file

* skip a format

* [CodeStyle][F401] remove unused import in python/paddle/distributed

* remove pass

* empty commit

* Fix ValueError: list.remove(x): x not in list for meta_optimizer_names.

Fix ValueError: list.remove(x): x not in list for meta_optimizer_names.

* Fix split import.

Fix split import.

* add noqa after meta_optimizers in factory

* restort collective ops

* expand `import *`

* add noqa after required imports

* try to fix APIs without core.ops

* Revert "try to fix APIs without core.ops"

This reverts commit 6172beaf601e84bf61f2490c12c4739f0edaa5eb.

* fix an increment

* empty commit

* add noqa after required imports

* expand `import *`, fix ci error
Co-authored-by: NShuangchi He <34329208+Yulv-git@users.noreply.github.com>

* 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

* update

* fix bugs

* modify code style

* fix bugs of _get_global_group

* merge latest develop branch

* fix bugs

* update

* fix bugs for unittest

* modify for less use of gpu mem

* fix bugs of using _reset_grad_inplace_version

* update

* update

* modify for CI-Coverage

* retrick all CIs