Add backward Int8Quantize shape inference (#34152)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/34152
Propagate the input shape of Int8Quantize backwards.
Test Plan:
```
buck test caffe2/caffe2/opt:bound_shape_inference_test
```
Reviewed By: csummersea
Differential Revision: D20231521
fbshipit-source-id: a77c61b0d5bc570241e62553cecd9ff38553ff44
