Keep manual_kernel_registration only effective in aten codegen. (#42386)
Summary:
This PR removes manual registration in aten/native codebase.
And it separates manual device/catchall kernel registration from manual VariableType kernel registration.
The first one remains as manual_kernel_registration in native_functions.yaml.
The second one is moved to tools/ codegen.
Difference in generated TypeDefault.cpp: https://gist.github.com/ailzhang/897ef9fdf0c834279cd358febba07734
No difference in generated VariableType_X.cpp
Pull Request resolved: https://github.com/pytorch/pytorch/pull/42386
Reviewed By: agolynski
Differential Revision: D22915649
Pulled By: ailzhang
fbshipit-source-id: ce93784b9b081234f05f3343e8de3c7a704a5783
