* [Demo] custom kernel based on pten kernel

* merge and npu custom work well

* del comments

* delete other code

* fix CUDAContext

* fix not found small_vector.h

* support NPU

* fix NPUContext

* fix DeviceContext support

* add UT

* fix call

* add UT

* fix

* fix for comments and ut

* add MACRO control

* fix multi input output

* support env CUSTOM_DEVICE_ROOT

* deal with special cases

* fix for Windows

* try coverage with test_custom_kernel_dot.py

* fix test_custom_kernel_dot

* fix test_custom_kernel_dot

* fix merge

* fix merge

* fix CI

* update

* merge and fix

* remove WITH_CUSTOM_KERNEL

* fix merge

* merge and fix

* fix ut

* fix ut for mac

* add more UT

* add more UT

* fix

* delete gloo connect retry

* the_one_ps dirs reconstruct

* .

* .

* create the_one_ps dirs

* create the_one_ps dirs

* create the_one_ps dirs

* create the_one_ps dirs

* create the_one_ps dirs

* create the_one_ps dirs

* the one ps dirs modify

* the one ps dirs modify

* the one ps dirs modify

* the one ps dirs modify

Integrated Trainer of Parameter Server (API add `fluid.contrib.layers.sparse_embedding` only) (#22957)

* Integrated Trainer of Parameter Server

* add paddle.fleet.DistributedStrategy for 2.0

do some odd jobs, test=develop

* add launch mp distributed mode module test=develop

* delete unused file test=develop

* refine usage test=develop

* refine usage test=develop

* move distributed package test=develop

* add to whl package test=develop

* Init slim.

* Remove distillation demo.

* Fix import errors.
test=develop

* Fix some issues.
test=develop

* Fix configs.
test=develop

* Modify API.spec.
test=develop

* Fix format.
test=develop

* Fix format.
test=develop

* Add some comments.

ISSUE=4586495

git-svn-id: https://svn.baidu.com/idl/trunk/paddle@1408 1ad973e4-5ce8-4261-8a94-b56d1f490c56