update code examples for paddle.sums 

* add size method for large scale

* add large scale UT

* add ut for checkpoint

* test=develop, fix geo sgd communicator

* test=develop, gloo_init_method

* test=develop, bug fix for gloo http_init

* test=document_fix

* fix slice doctest=document_fix

* test=document_fix

* test=document_fix

* test=document_fix

* test=document_fix

* raise error if use multi-cards in fleet non_distributed mode; test=develop

* add reduce xpu op test=develop;test=kunlun

* add reduce xpu op test=develop;test=kunlun

* add reduce xpu op test=develop;test=kunlun

* add reduce xpu op test=develop;test=kunlun

* add reduce xpu op test=develop;test=kunlun

* add tensor clone

* fix unittest test_var_base

1. support channel last in BatchNorm*d (#27875)
2. fix a bug in batch_norm_op cuda kernel by extracting ResizeToChannelFist(Last), TransToChannelFirst(Last) to operators/layer_utils.h

* step lr_scheduler on epoch end in hapi/model.py fit. test=develop

* fix DataLoader single process mode exit SIGABRT error. test=develop

* Implement the function of OueScaleForTraining/OutScaleForInference in dygraph

test=develop

* fix hapi load

* 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

* fix test directory migration

* change assert to self.assertXXX

* support setting xpu place

* add ut, test=kunlun

* del the DEFINE_ALIAS of sigmoid_cross_entropy_with_logits

* del sigmoid_cross_entropy_with_logits in python/paddle/nn/functional/loss.py, test=develop

* call paddle.fluid.layers.sigmoid_cross_entropy_with_logits in bce_with_logits_loss, test=develop

* fix adam

* fix gpu adam

* fix code style

* fix ut

* update ut add cuda code

* add stack pool2d roi_align xpu op,test=kunlun

* error message opt, test=kunlun

* add xpu unittest,test=kunlun

* skip check grad,test=kunlun

* fix boostget , test=kunlun

fix the dataset remove bug for the dataset 

Add elementwise XPU OP kernel for KUNLUN core, including (but still cannot process common broadcast

* refine to_string

* re-enable ut

* remove image_resize series api in Paddle2.0

* update assign/cast/linspace/addcmul op doc for 2.0 api,test=document_fix

* fix bug about cast doc for 2.0 api,test=document_fix

* Add api of constant in paddle.nn.initializer

* Add api of constant in paddle.nn.initializer

* Add api of constant in paddle.nn.initializer

* Add api of constant in paddle.nn.initializer

* Add api of constant in paddle.nn.initializer

* Add api of constant in paddle.nn.initializer

* Add api of constant in paddle.nn.initializer

* Add api of KaimingUniform & KaimingNormal in paddle.nn.initializer

* Add api of KaimingUniform & KaimingNormal in paddle.nn.initializer

* Add api of KaimingUniform & KaimingNormal in paddle.nn.initializer

* Add api of KaimingUniform & KaimingNormal in paddle.nn.initializer

* Add api of KaimingUniform & KaimingNormal in paddle.nn.initializer

* Add api of KaimingUniform & KaimingNormal in paddle.nn.initializer

* test=document_fix

* test=document_fix

* add sparse tensor load method

add paddle.nn.initializer API, including: Normal, TruncatedNormal, Uniform, XavierNormal, XavierUniform, Assign (#27769)

* test=develop, bug fix for parameter_recv
* test=develop, for unittest, test_fleet_rolemaker_new

*test=kunlun

* add multitask

* add multitask, test=develop

* fix code style, test=develop

* add partail push dense, test=develop

* fix has_kay in py3, test=develop

* fix, test=develop

* fix, test=develop

* fix, test=develop

* 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