[Quant] Add fused conv2d_add op for onednn backend (#90262)
**Summary**
Post op fusion can reduce data movement overhead and improve inference performance. This PR adds fused `conv2d_add` op for onednn backend, which will be used for int8 inference with onednn backend. Cannot call this op with other quantization backends otherwise an error is thrown.
**Test Plan**
```
python -m pytest test_quantization.py::TestQuantizedConv
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/90262
Approved by: https://github.com/jgong5, https://github.com/jerryzh168
