* support auto fallback to  cpu kernel for cusom device

* fix some problem of kernel fallback

* 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

* update

* remove useless code

* remove label smooth test

* polish code

* polish code

* polish code

* remove _in_eager_mode error;

* fix selected_rows bug in C++ API

* add optional for C++ APIO

* data transform support optional

* remove data transform for optional vector<Tensor>

* adjust some format of funtcion

* fix empyt bug

* rename pten dir to phi

* rename namespace to phi

* rename infrt pten dir to phi

* resolve conflict

* rename pten to phi in cmake

* revert all infrt change

* change needed files

* fix infrt failed

* fix inference failed

* add data_transform in pten api

* support GetKernelTypeForVar

* fix complie problem of bfloat16

* change error namespace

* add complex type transform unittest

* fix merge conflict