* Refactor MKL-DNN ElementwiseMul

remove manual fallback, remove format attrs
test=develop

* Refine PADDLE_ENFORCEs in eltwise_mul_op.h

test=develop

* Make ElementwiseMulOp inherit from ElementwiseOp

* Change type of simd_width to int

test=develop

* Remove Constructor extensions in ElementwiseOp and ElementwiseMulOp

test=develop

* Restore attributes

test=develop

* Fix test coverage for mkldnn eltwise mul

test=develop

* Conform to new is_run_common_broadcast API

test=develop

* Add UT for AreDimsAndFormatCorrect

test=develop

* update elementwise double grad to save gpu memory, test=develop

* update elementwise_mul/div_grad_grad to save memory, test=develop

* remove eval function in eigen statement to save memory, test=develop

* add unittest for elementwise_div_grad_grad without dout, test=develop

* add unittest for elementwise_add_grad_grad without ddx, test=develop

* add float16 cuda kernel for elementwise double grad op, test=develop

* add_elementwise_add_inplace_test,test=develop

* rename file, test=develop

* wip simplify operator framework

* wip

* wip

* done test=develop

* clean test=develop

* fix test=develop

* fix deps test=develop

* fix cpu build test=develop

* fix tensorrt build test=develop

* fix tests test=develop

* fix test=develop

* fix cpu build test=develop