[quant][graphmode][fx] Add reference quantized linear module (#63627)

[quant][graphmode][fx] Add reference quantized linear module (#63627)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/63627

Added reference quantized linear module for the custom backend flow, the reference quantized module will
have the following code:
```
        w(float) -- quant - dequant \
        x(float) ------------- F.linear ---
```
In the full model, we will see
```
        w(float) -- quant - *dequant \
        x -- quant --- *dequant --  *F.linear --- *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: D30504750

fbshipit-source-id: 5729921745c2b6a0fb344efc3689f3b170e89500