[fx2trt] example for lowering model to trt with FX based tooling (#57298)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57298
Some of the code is borrowed from NVIDIA-AI-IOT/torch2trt https://github.com/NVIDIA-AI-IOT/torch2trt/tree/master/torch2trt.
Move fx2trt stuff to fx/experimental/fx2trt.
Add an example in fx/experimental/fx2trt/example/fx2trt_example.py that shows how we lower resnet18 to TensorRT using FX.
TODO: Include license from NVIDIA-AI-IOT/torch2trt
Test Plan: CI
Reviewed By: jackm321
Differential Revision: D28102144
fbshipit-source-id: 1a7b03e45b8ab3fcc355d097d73afeec2efc3328
