* add pure fp16 major function in auto_cast & tracer

* support master weight in dygraph for pure fp16

* check mix dtype of fp16&fp32 for check_finite_and_unscale op

* change pure fp16 funtion name

* refine some bug in auto_cast

* refine auto_cast interface logic

* add param _casted_by_pure_fp16 for class Layer

* support state_dict hook for save model by user appointed dtype in pure_fp16_decorator

* refine pure_fp16_decorator as decorator

* add unittest

* add comment

* add comment

* support recompute

* add comment for auto_cast and decorator

* support to_static_state_dict for paddle.jit.save

* unlimite models num and optimizers num

* add lookup_table in black_list

* fix momentum and layer state_dict

* fix bug in layer state_dict

* fix bug in layer state_dict_helper

* refine unittest

* refine test_momentun_op

* refine interface and some code

* refine amp_decorator interface

* refine pure fp16 interface

* refine master weight interface

* Add solutions to PyLayer which is unsupported in DataParallel

* modify note format for parallel.py

* modify docs of dataparallel

* add docs of dp with pylayer

* modify docs format

* modify example format

* change example of dp with pylayer

* add unittest for dp with pylayer

* modify ut

* merge latest codes

* update

* modify for CI-Coverage

* modify text-indent

* support hybrid parallel inference helper class

* fix hdfs and fleet_util for supporting save/load infer;test=develop

* dygraph sharding

* update unitest hybrid_parallel_communicate_group

* del py2 code2

* fix test timeout

* Dygraph Recompute support AMP

* dygraph recompute: update unitest

* fix precision of mp

* fix bug of seed

* fix dp

* print group

avoid polluting logging's root logger

* fix model parallel

* rm parallel_help.py

* add embedding

* Dygraph reocmpute

* unitest for Dygraph reocmpute

* dy recompute remove unitest for win and mac

* add pipeline layer

* add clip/check

* add amp & clip grad in dygraph

* add logging

* support dp & mp

* add PullSparseValue for pull sparse

* fix bug for PullSparseValue

* add test mode in lookuptable

* revert API change

* add comment for is_training

* topo and memory performance for heterps; test=develop
* add trainwithprofiler in heter trainier; test=develop

* test=develop, add distributed_infer

* oneps (3/4)
Co-authored-by: NMrChengmo <cmchengmo@163.com>
Co-authored-by: Nmalin10 <malin10@baidu.com>
Co-authored-by: Nchengmo <chengmo@baidu.com>

* update, test=develop

* test=develop, rm pathlib

* update, test=develop

* add gloo initializer, test=develop

* set default value to strategy in distributed_optimizer test=develop

* add gloo initializer, test=develop

* test=develop, bug fix

* test=develop, util documents

* fix api document

* move paddle.fleet to paddle.distributed.fleet