Add common_fx2trt.py (#66579)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/66579
Didn't commit this file in the PR that open sources fx2trt tests
Test Plan: ci
Reviewed By: 842974287
Differential Revision: D31623354
fbshipit-source-id: 6cedbe0f229da40499b83e6df28e16caca392d9c
