* combine reduce_cuda codes

* support float16 in pten redcue_mean

* replace ReduceCudaKernel impl with pten reduce impl

* mv reduce funcs into reduce_cuda_impl

* rm unsed codes and headers

* mv GetReduceDim into reduce_cuda_impl

* recover GetReduceDim in reduce_op.h

* add new dispatch macro

* fix pool op output not inited and cause transform to pten::denseTensor error

* fix output tensor not initialized error

* rename new dispatch macro and format code style

* rm reduce_functor_op.h file

* move dot kernel impl

* remove needless cmake items

* add pten kernel cmake

* add pten kernel cmake function

* fix compile error

* add enforce include for full kernel

* fix compile failed

* change cuda to gpu

* fix cmake function error

* move flatten

* fix bugs of test

* modify header file

* add copy declare

* fix compile bugs

* rename cuda to gpu

* revert CMake change

* resolve conflit

* rename other cuda to gpu

* poish details