* add legacy_api.yaml

* set merged_momentum inplace only

* support inplace optional<vector<tensor>>

* add dygraph_mode api

* optimize TensorToConstDenseTensorPtr

* support optional<vector<Tensor>> in yaml and eager

* delete useless comments in eager_gen.py

* fix api_base.py support optional<vector<TTensor>>

* python_c_gen.py support optional<vector<tensor>>

* transfer linear_interp_v2 yaml from fluid to phi

* fix op_test typo error

* change linear_interp_v2 testcase

* fix args in final_state_linear_interp_v2

* fix zeropad2d typo. test=document_fix

* support complexd selected_rows kernel in yaml

* support configuring optimizer api in yaml

* fix data transform bug

* refactor the optional tensor

* remove optiona<MetaTensor> in InferMeta

* fix bug

* fix optional<vector<Tensor>>

* fix bug

* fix rmsprop

* fix amp of eager_gen

* polish code

* fix deleted code

* fix merge conflict

* polish code

* remove is_nullopt_

* fix merge conflict

* fix merge conflict

* remove storage

* add glog include

* add glog include

* add glog include

* change the output format of C++ backward api

* fix merge conflict

* fix sparse api code auto-gen

* fix eager_gen bug

* fix bug of output is null

* fix bug of conv2d_grad_impl

* fix optional grad

* fix bug of eager-gen double_grad

* fix bug

* fix multiply_double_grad bug

* remove node pruning

* add sgd yaml

* change python api

* open eager mode in sgd

* fix bug

* support setting vector out size in yaml

* support setting size of vector<tensor> for out in yaml

* fix eager gen opti bug

* polish code

* fix some bug

* fix some bugs;

* add string tensor and case convert kernels

* Add strings empty kernel; Reorganize the structure of case convert kernel

* Add string infermeta

* Update mutable_data of string tensor

* rename kernel name

* add string copy tmp

* Fix strings copy device bug

* add utf8 gpu converter

* add string tensor c++ api

* Remove mutable_data of string tensor

* update string tensor interface

* remove charcases_flag.h

* remove some fluid headers

* Add make_ddim

* __HIPCC__ -> PADDLE_WITH_HIP

* remove fluid headers

* fix cpu compile

* remove std::hash

* Fix cudaMalloc

* Remove strings/impl directory

* Fix infrt/get_phi_kernel_info.py;Add custom_kernels deps

* Add empty kernel test

* Remove some comments

* Modify lower/upper api encoding type: string->bool

* STRING->PSTRING; Add CreateInferLikeMeta

* Add code gen for C++ String API

* remove strings_api_utils.h

* Add ignore file (strings_api.h, strings_api.cc)

* update strings gen script

* change args order of case convert kernels

* Add comments for pstring, StringTensor

* cpstring_internal.h -> cpstring_impl.h

* Update accordding to comments:

1. Remove fluid headers
2. paddle::platform::errors -> phi::errors
3. Use 'place.GetType() == phi::AllocationType::GPU' instead of 'paddle::platform::is_cpu_space()'
4. Use camel code style

* Remove all singletons in strings kernels

* fix rocm compile

* Fix py3 compile

* Fix c++ coverage

* 1. Add pstring proto type
2. Add StringTensor debug info
3. Rename case_convert_kernel to strings_lower_upper
4. Remove serialize derialize strings kernel

* DataLayout::PSTRING -> DataLayout::PSTRING_UNION

* Register pstring data type

* Fix strings api gen

* Fix dense tensor register pstring dtype

* Fix error messages

* remove line

* add pstring unittest

* remove test string api unitest

* remove empty line

* Remove some headers to decrease the size of executable file

* change input vec tensor to pointer

* update input between

* fix format error

* resolve conflict

* resolve conflict

* suppport sparse api in yaml

* support auto-gen code of sparse api

* do some refactor

* add unittest test_sparse_conv_api

* add unitest file
Co-authored-by: Nzkh2016 <zhangkaihuo@baidu.com>