* 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

* rename cuda to gpu

* revert CMake change

* resolve conflit

* rename other cuda to gpu

* poish details

* fix when out_dtype is same with x.dtype and still transform type error

* fix spell error

* fix_bugs_for_elementwise_branch_selection

* fix merge_dims bugs

* fix all influenced file

* unify device context entrance

* move all_context include to header

* polish cmake relay for device_context

* fix npu compile failed

* fix npu compile failed

* fix pten::Copy use error in redcue_impl

* remove in_dtype args in reduce kernel

* fix copy error

* fix copy error