* 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

* first commit

* fix compile error

* support std::vector<std::srting>

* fix

* fix op support on GPU by chenweihang

* pass test

* infershape

* add set_dtype

* fix order

* fix

* unify the impl of dt and sr

* fix