* modify cond while_loop to paddle.static.nn.cond

* modify crop_tensor to paddle.crop

* modify Variable to paddle.static.Variable

* remove nn.beam_search, nn.beam_search_decode, nn.gather_tree

* remove bpr_loss, center_loss, rank_loss, smooth_l1, teacher_student_sigmoid_loss, edit_distance, sampled_softmax_with_cross_entropy in nn.functional

* remove apis in nn.functional.learn_rate.py

* remove pool2d, pool3d, adaptive_pool2d, adaptive_pool3d in nn.functional

* remove apis in nn.functional.vision

* remove erf, soft_relu in nn.functional.activation

* remove apis in nn.functional.extension

* remove nn.functional.rnn

* remove hash from nn.functional.lod

* remove row_conv from nn.functional.extension

* remove one_hot, pad2d, pad_constant_like from nn.functional.common

* remove nn.gather_tree, nn.BilinearTensorProduct, nn.Pool2D, nn.Pad2D

* remove apis from optimizer.__init

* remove tensor.creation.fill_constant

* remove elementwise_mul in nn.functional.common and  modify to paddle.multiply

* remove  tensor.stat.reduce_mean

* remove reduce_all, reduce_any in tensor.logic

* remove apis in tensor.math

* remove apis in tensor.__init__

* remove has_inf, has_nan in tensor.search

* remove apis in framework.__init__

* remove apis in paddle.__init__

* remove apis in nn.functional.__init__

* modify removed alias apis to raw api in doc and unittests

* fix remove grid_sample bug

* modify removed alias apis to raw api in doc and unittests

* modify removed alias apis to raw api in doc and unittests

* modify removed alias apis to raw api in doc and unittests

* modify removed alias apis to raw api in doc and unittests

* modify removed alias apis to raw api in doc and unittests

* modify removed alias apis to raw api in doc and unittests

* delete alias api relastions in doc

* reserve paddle.compat, paddle.sysconfig

* remove unittest for paddle.reduce_all, paddle.reduce_any

* modify removed alias apis to raw api in doc and unittests

* recover paddle.save and paddle.load

* resolve conflicts

* fix sample code missing paddle.enable_static() bug

* fix sample code missing paddle.enable_static() bug

* fix to_string sample code error

* remove image_resize series api in Paddle2.0

* fix norm api doc, test=develop

* fix error message, test=develop

* fix api norm, test=develop

* add adagrad, test=develop

* fix bug, test=develop

* fix bug, test=develop

* add spetral_norm, test=develop

* fix adagrad, test=develop

* merge , test=develop

* 1. remove paddle.unique_with_counts api, which counts as unique api
2. add paddle.math.increment(x, value=1.0, name=None) api
3. replace paddle.sums with paddle.add_n api
4. update paddle.metric.accuracy api (add name parameter)

Update code examples for api2.0 

* refine parameters order && doc

* update rmsprop doc

* refine adam/transpose/unstack/stride_slice

* fix bug && doc

* fix doc

* bug fix

* bug fix

* fix doc

* fix doc

* fix doc

* fix doc

* depercate old strided_slice

* update doc

* set default value for name

* update doc

* Fix ErrorClipByValue api and demo code of clip_by_value. test=develop
Co-authored-by: Ntianshuo78520a <707759223@qq.com>

* refine grid_sample and temporal_shift

* update 2.0 API for dice_loss and log_loss test=document_fix

* fix the scatternd/scatterndadd

* fix the doc of scatter

* replace rank with ndim

* migrate code example and doc

* remove inplace argument

* fix sample code

* fix sample code

* modified sample code of add_position_encoding to  2.0, test=document_fix

* use core.op in add_position_encoding API.

* add test for add_position_encoding in dygraph mode

* fix example code

* rename var to tensor

* remove static

* fix return type

* add double grad compute for batch norm,test=develop

* fix unittest, test=develop

* remove unuse tensor,test=develop

* add format,test=develop

* update, test=develop

and optimize the c++ implmentation of empty op as PR#26659 reviews,
and add bool for shape op.

* enhance collect_op for dygraph, test=develop

* enhance detection ops with lod, test=develop

* support none bbox left in generate_proposals, test=develop

* unfiy MultiLevelRoisNum, test=develop

* update core.ops, test=develop

* add op register for new input & output, test=develop

* delate some wrong message test=develop, test=document_fix

* delate some wrong message

* fix unsqueeze in dygraph

* add test

* add test

update doc of paddle.to_tensor

* refine paddle.stack

* support TensorArray

* add test

* fix coverage problem

* fix coverage problem

* fix sample code

As the title

* add embedding 2.0

* add embedding support input int32

* set default dtype for distribution API

* Add unittest

* Add unittest

* fix import get_default_dtype problem

* delete change under fluid.layers.nn

* little change

* add deprecated, test=develop

add broadcast feature for elementwise logical op

* update doc, test=document_fix

* add attr(dtype)

* refine code