[quant][graphmode][fx] Add reference quantized conv module (#63828)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/63828
Added reference quantized conv module for the custom backend flow, the reference quantized module will
have the following code:
```
w(float) -- quant - dequant \
x(float) ------------- F.conv2d ---
```
In the full model, we will see
```
w(float) -- quant - *dequant \
x -- quant --- *dequant -- *F.conv2d --- *quant - dequant
```
and the backend should be able to fuse the ops with `*` into a quantized linear
Test Plan:
python test/test_quantization.py TestQuantizeFx.test_conv_linear_reference
Imported from OSS
Reviewed By: vkuzo
Differential Revision: D30504749
fbshipit-source-id: e1d8c43a0e0d6d9ea2375b8ca59a9c0f455514fb
