Enable lowering to inductor (#96927)
**Summary**
Enable the lowering path from a quantized 2.0 fx graph into Inductor. The basic usage will be
```
export_module, guards = torchdynamo.export(m, *args)
prepare_module = prepare_pt2e(export_module, *args)
convert_module = convert_pt2e(prepare_module)
ooptimized_module = compile_fx(convert_module, example_inputs)
```
Most of the issues we met previously has already been fixed in PyTorch Master. So in this PR, we mainly do 2 things:
1. Add the basic usage into a UT.
2. Move `handle_dynamo_export_graph` before the fusion passes, otherwise the dynamo_export_graph will hit the fusion passes twice which is un-expected.
**Test Plan**
```
clear && python -m pytest test_quantization.py -k test_inductor_backend_config_conv
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/96927
Approved by: https://github.com/jgong5, https://github.com/EikanWang, https://github.com/jansel, https://github.com/jerryzh168
