GitLab

Summary:
Added predictor_type `boltnn_int8` to export to BoltNN via torch delegate.

- `int8` needs to be in the name, otherwise the post-train quantization won't happen;

```
cfg.QUANTIZATION.BACKEND = "qnnpack"
// cfg.QUANTIZATION.CUSTOM_QSCHEME = "per_tensor_affine"
```

Seems that ` QUANTIZATION.CUSTOM_QSCHEME per_tensor_affine` is not needed - likely covered by "qnnpack".

Reviewed By: wat3rBro

Differential Revision: D29106043

fbshipit-source-id: 865ac5af86919fe7b4530b48433a1bd11e295bf4