* [Eager] Fix paddle.grad interface

* [Eager] Support minimum SubGraph for GeneralGrad

* Add needed_nodes to prune grad graph more thoroughly

* [Eager] Add grad_node_trans_mapping_ to record which grad_node has been transformed to AccumulationNode

* [Eager] Fix paddle.grad interface

* Polish code

* remove potential_stop_node

* Add endding_nodes to enhance genSugraph logic

* clear endding_nodes_

* polish code

* rename endding_nodes to endding_nades_

* Refactor grad interface

* Add register_hook case to fix coverage-ci

* Fix code format

* Refactor general_grad

* Add more code comments

* call clear directly to release GradSlotMeta

* fix a mistake

* fix matmul/ multiply kernel logic and optional input in yaml, fill zeros logic and so on.

* fix batch_norm_double_grad yaml optional config

* fix tanh_triple_grad yaml and kernels

* fix MultiplyTripleGradKernel optional logic

* fix merge mistake

* fix compile error

* remove legacy attr for bn

* polish code

* fix some kernel

* merge develop

* fix error

* remote log

* fix kernel with full like

* hide value log behind

* hide value log behind

* fix matmul_triple grad
Co-authored-by: NWeilong Wu <veyron_wu@163.com>