This reverts commit 9e4fe923.

* fix doc

* test=develop

* test=develop

* test=develop

* test=develop

* test=develop

* test=develop

* test=develop

* test=develop

* fix doc, test=develop

* update localsgd doc
test=develop

* update localsgd doc
test=develop

* fix fleet dgc amp doc, test=develop

* fix, test=develop

* fix async configs
Co-authored-by: Nliuyi05 <gavin1332@gmail.com>
Co-authored-by: NWangXi <wangxi16@baidu.com>
Co-authored-by: NseiriosPlus <tangwei12@baidu.com>

* fix api document

* modified timeout value on windows and mac (#26690)

* add Local SGD algorithm referenced paper
test=develop

* add cudnn related strategies to DistributedStrategy

* add documentation for DistributedStrategy

* add feature to fleet2.0 role_maker, distribute_strategy, test=develop

* move paddle.fleet to paddle.distributed.fleet

add lamb to fleet meta optimizer

* add paddle.fleet.AsyncOptimizer
Co-authored-by: Ndongdaxiang <dongdaxiang@baidu.com>

Add dgc to fleet meta optimizer, rm dgc from optimizer all

* split meta optimizer files
* add graph execution in execution, update two properties in DistributedStrategy, unit tests for these features

* add gradient Merge optimizer to meta, test=develop

* refine strategy compiler and meta optimizers
make async as a_sync

* add more settings for distributed strategy
Basically, DistributedStrategy has several parts of configurations:
- BuildStrategy: the same as paddle.fluid.BuildStrategy, but the distributed arguments are moved out of BuildStrategy
- ExecutionStrategy: the same as paddle.fluid.ExecutionStrategy
- collective communication configs: nccl_comm_num, hierarchical allreduce and so on
- distributed algorithms: async_update(mainly used in PS), lars, lamb and so on

refactor fleet api under paddle.fleet
update DistributedStrategy

test=develop

* add paddle.fleet.DistributedStrategy for 2.0