Add Code Generation for operators, op makers and argument mapping functions

[iclementine]

PR types

Others

PR changes

Others

Describe

1. add api yaml vadilation for forward and backward apis;
2. add code generation of operators, opmakers and argument mapping functions;
3. add a default constructor for Scalar to avoid compilation error of backward nodes;
4. add new_api.yaml and new_backward.yaml as a place holder for new apis, which are also included in c++ api generation and dygraph function generation.

For phi kernels to generate operator and argument mapping function for, put those api yaml in new_api.yaml and new_backward.yaml.

All the api entries in api.yaml, new_api.yaml, backward.yaml, 'new_backward.yaml` would be parsed and validated.

If there is any apis to genrate operator and argument mapping function, there would be a paddle/fluid/operators/generated_op.cc and paddle/phi/ops/compat/generated_sig.cc.

[paddle-bot-old]

Sorry to inform you that 1b0720a's CIs have passed for more than 7 days. To prevent PR conflicts, you need to re-run all CIs manually.

[XiaoguangHu01]

LGTM

[XiaoguangHu01]

LGTM