* fix the docs bug in collective file

Fix the bug in paddle.distributed.split demo. The paddle.distributed.split op just can be used in static mode. (#34306)

* fix the bug in paddle.distributed.split demo

* add wait_server_ready

* fix remove bug

* fix the bug that happened in alltoall in dygraph mode

* cache core.ops, test=develop

* refine, test=develop

* add scatter-gather opt

* fix topo for pp

* rename function

* kill process by group

* opt dygraph python code, test=develop

* refine, test=develop

* pipeline adaptive for heterps;test=develop
* fix finalize hang;test=develop
* add is_compiled_with_heterps for dataset;test=develop
* fix hashtable core when pass ins_num=0;test=develop

* add amp support for pp

* add amp untest

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

* add random and prevent deadlock

* dygraph sharding

* update unitest hybrid_parallel_communicate_group

* elastic unitest

* rename demo

* del py2 code2

* fix test timeout

* elastic etcd ready