Create BackendTransformerBase to host common functions used for backend lowering (#17074)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/17074
There are some common functionalities in backend lowering. This diff creates a base class which hosts these common stuff.
Reviewed By: ipiszy
Differential Revision: D14073192
fbshipit-source-id: 9617603d0e73db6f7fcc5572756b9dbab506dae5
