* dygraph sharding

* update unitest hybrid_parallel_communicate_group

* elastic unitest

* rename demo

* del py2 code2

* fix test timeout

* elastic etcd ready

* add pplayer

* add sharedlayerdesc

This reverts commit b2afc8df.

* update spawn doc for xpu, test=ducument_fix

* add note for gpu and xpu, test=document_fix

* update 2.0 public api in all left files

* reverse device.py all list;
fix some flake8 errors

* fix Undefined variables

* fix Undefined variables

* update, test=develop

* add parallel_cross_entropy

* add grad for crossentropy

* fix cross entropy

* modify API nn.Bilinear's doc, test=develop

Add 'self' parameters to function Cluster::update_pods, use variable name 'cur_proxy' instead of 'proxy' in file 'tools/get_pr_ut.py' (#33377)

* undefined variable proxy

* Cluster::update_pods lacks of parameter self

* fix c_split bug

* fix utest

* add c_embedding for tensorparallel

* fix hang of hybrid parallel

* fix new_group for hang problem

* Dygraph Recompute support AMP

* dygraph recompute: update unitest

* update mp

* fix spawn default nprocs get error

* polish error message

* support ssd in PsCore

* remove log

* remove bz2

* defalut value

* code style

* parse table class

* code style

* add define

* add async save for sparse table
* add load profiler for sparse table
* add load info for sparse table