Dev functional interface. (#4932)

* Dev functional interface.

* Remove repeated function_traits

* Implement add and add_scalar static functional op.

* Remove unused code

* Refactor

* Refine

* Generate and export functional apis.

* Refine

* Refine

* Refine

* Generate functional api and pybind cpp when building the project.

* Refine code style and implement normalization functor.

* Fix cmake

* Add PyYAML requirement.

* Add JUST

* Fix scalar IsIntegral and IsSigned

* Add scalar add grad func.

* Fix norm grad func to support dynamic attrs.

* Support DataType.

* Recursive determine input tensors.

* Update generate_functional_api.py

* Fix conversion from python object to dtype.

* Fix crash since function has been cast with wrong function signature, the converted function behavior is undefined.

* Check and throw error.

* Refine

* Use Maybe instead of throwing exception directly.

Co-authored-by: oneflow-ci-bot <69100618+oneflow-ci-bot@users.noreply.github.com>