* refine paddle inference api
Co-authored-by: Nnhzlx <nhzlx.dragon@gmail.com>

* add api to clear intemediate tensors in analysis predictor. test=develop

* add python api. test=develop

* Add a interface to enable cudnn for inference.

* Add cudnn_placement_pass.
test=develop

* Set the default value of cudnn_enabled_op_types to null.
test=develop

* Write the common basic class, placement_pass_base, to refine the codes.
test=develop

* Call EnableCUDNN in unittest.
test=develop

* Refine cudnn_placement_pass tester.

* Enable the testing of cudnn_placement_pass in inference's unittest.
test=develop

* Add the check of op kernels.
test=develop

test=develop