Remove autograd/grad api (#35579)

* remove autograd/grad api

* import grad, no_grad set_grad_enable from autograd module

* modify import no_grad_ as no_grad

python/paddle/__init__.py

@@ -255,9 +255,9 @@ from .framework import CUDAPlace  # noqa: F401
 from .framework import NPUPlace  # noqa: F401
 from .framework import CUDAPinnedPlace  # noqa: F401
 
-from .framework import grad  # noqa: F401
-from .framework import no_grad  # noqa: F401
-from .framework import set_grad_enabled  # noqa: F401
+from .autograd import grad  # noqa: F401
+from .autograd import no_grad  # noqa: F401
+from .autograd import set_grad_enabled  # noqa: F401
 from .framework import save  # noqa: F401
 from .framework import load  # noqa: F401
 from .framework import DataParallel  # noqa: F401

python/paddle/autograd/__init__.py

@@ -16,5 +16,7 @@ from ..fluid.dygraph.base import grad  # noqa: F401
 from . import backward_mode  # noqa: F401
 from .backward_mode import backward  # noqa: F401
 from .py_layer import PyLayer, PyLayerContext  # noqa: F401
+from ..framework import set_grad_enabled  # noqa: F401
+from ..fluid.dygraph.base import no_grad_ as no_grad  # noqa: F401
 
-__all__ = ['grad', 'backward', 'PyLayer', 'PyLayerContext']
+__all__ = ['backward', 'PyLayer', 'PyLayerContext']