[quant][graphmode] initial support for fusion pattern in backend_config_dict (#69335)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69335
This PR added support for configuring fusion with:
"pattern", "fuser_method"
This only works for simple sequence of 2 op patterns currently, will extend this in future PRs
Test Plan:
regresion test on linear-relu fusion:
```
python test/fx2trt/test_quant_trt.py TestQuantizeFxTRTOps
```
Imported from OSS
Reviewed By: vkuzo
Differential Revision: D32816164
fbshipit-source-id: f300b7b96b36908cb94a50a8a17e0e15032509eb
