quantization: fix scale+zp serialization of quantized BatchNorm{2|3}d (#70432)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/70432
Scale and zero_point need to be buffers for serialization to work
on them properly. This PR moves them to buffers. This is BC breaking,
but the "before" state was completely broken (scale + zp were not
serialized at all) so there is no value in trying to handle it.
Test Plan:
```
python test/test_quantization.py TestStaticQuantizedModule.test_batch_norm2d_serialization
python test/test_quantization.py TestStaticQuantizedModule.test_batch_norm3d_serialization
```
```
python test/test_quantization.py TestStaticQuantizedModule.test_batch_norm2d_serialization
```
Imported from OSS
Differential Revision:
D33330022
D33330022
Reviewed By: jerryzh168
Pulled By: vkuzo
fbshipit-source-id: 673c61f1a9f8f949fd9e6d09a4dbd9e5c9d5fd04
