**Summary**
This PR adds a lowering pass for x86 backend
- Patterns of `dequantize -> conv/linear (-> quantize)` are fused to corresponding quantized onednn ops.
- Weights are prepacked ahead of time.
- Post ops of conv/linear are fused if supported.
- The pass returns a `GraphModule` with the modifications mentioned above.
**Test plan**
```
pytest test/quantization/pt2e/test_x86inductor_quantizer.py -k test_lowering_to_x86
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/149708
Approved by: https://github.com/jerryzh168, https://github.com/leslie-fang-intel
3b0cd9b542