* rename cuda to gpu

* revert CMake change

* resolve conflit

* rename other cuda to gpu

* poish details

* add register_ctx_kernel and move scale kernel

* polish details by reviewer comment

* fix xpu compile failed

* fix cmake error

* add variadic_args kernel in pten

* merge develop code

* add variadic_args kernel and benchmark

* change dynamic_cast to static_cast for DeviceContext

* merge the code

* modify code format

* refactor variadic kernel function