This reverts commit 66fce9e8.

Fleet Parameter Server API Integrated

* fix add grad bug test=develop

* update style test=develop

* test=develop, optimize distributedstrategy

* add sync communicator and implement

pretty print for communicator flag

* add thread barrier for the compiled program

* update

* update test=develop

* update compile set test=develop

* update compile set test=develop

* update test=develop

* update test=develop

* update test=develop

* update compile setting test=develop

* update compile setting test=develop

* update run demo test=develop

* update test=develop

* update test=develop

* fix test=develop

* update test=develop

* update test=develop

* update test=develop

* update test=develop

* update test=develop

* update test=develop

* update test=develop

* update test=develop

* update test=develop

* update format test=develop

* update format test=develop

* update style test=develop

* update style test=develop

* change style test=develop

* change style test=develop

* change style test=develop

* add dataset unittest test=develop

* update test=develop

* update for record test=develop

* udpate style for record test=develop

* update for record test=develop

* update for record test=develop

* update for record test=develop

* fix format test=develop

* update test=develop

* update test=develop

* update test=develop

* update test=develop

* update test=develop

* add hdfs ls retry time and sleep time, fix save inference
* test=develop

* fix bug with half communicator

* add GeneralRoleMaker which is for general usage
* test=develop

* add half_async in the communicator
* fix DistributedStrategy

* add distributed_strategy

* fix fleet save bug of save_infernece_model
* test=develop

* fix some typos in AMP. test=develop

* delete useless codes. test=develop

* print table stat
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* notes
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* notes
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* fix fs_client_param bug， user can set this config through fleet_desc_file or fleet config
* test=develop

* general table

* add sparse table
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* no cvm
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* add no_cvm
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* add note
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* code style
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* code style
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* code style
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* code style
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* code style
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* add key of optimizer
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* solve pslib stop core
test=develop

* barrier
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* add notes
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* fix fleet util bug in save paddle inference model
* test=develop

* general table

* add sparse table
test=develop

* no cvm
test=develop

* add no_cvm
test=develop

* add note
test=develop

* code style
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* code style
test=develop

* code style
test=develop

* code style
test=develop

* code style
test=develop

* add key of optimizer
test=develop

test=develop

* fix cache table bug
* add save_paddle_inference_model
* fix hdfs util bug
* test=develop

* copy some feasigns and corresponding embeddings from one sparse table to another
* copy all feasigns and corresponding embeddings from one sparse table to another
* copy all dense params from one table to another
* copy some local vars to other local vars

modify the implementation of save_persistables and save_inference_model for fleet collective mode (#20802)

* modify the implementation of  save_persistables and save_inference_model functions for fleet collective, test=develop

* add ut, test=develop

test=develop

* fix PaddleCloud Role maker & add warning in distribute transpiler  & change rpc_retry_times

* support dump param to afs
test=develop

* code style
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* code style
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* dump param
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* dump param
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* dump param
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* dump param
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* no longer need to define all embedding layers (no one less) of all slots in each program. make trainer_param repeated in ps.proto.
* add find_distributed_lookup_table_grads instead of hard code GRAD
* support embedding stop gradient. push sparse has error before fix this.* 
* fix fill sparse, skip slots which do not have embedding. each slot's embedding in a sparse table should be used in all training programs before fix this.
* fix pull sparse, skip slots which do not have embedding.
* fix collect feasign label info, skip slots which do not have embedding.
* support when there are multi sparse tables in one or multi training programs, each program can pull/push its own related sparse tables instead of all sparse tables.
* test=develop

* add check nan / inf in downpour worker during training
* test=develop

* test=develop,Fix communicator slow bug

* test=develop, delete if() in stop_worker()

* test=develop

* fix UT, test=develop

* fix bug in fetch handler, test=develop

* fix bug in fetch handler, test=develop

* test=develop, fix fetch barrier bug

* test=develop, bug fix

* test=develop, bug fix

* test=develop, fix bug

* special case: strategy is None

* support dump multi file
test=develop

* dump fix num file
test=develop