hardsigmoid operator for QNNPACK, using LUTs (#36698)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/36698
Adds the hardsigmoid op to QNNPACK using the LUT kernel
Test Plan:
```
cd aten/src/ATen/native/quantized/cpu/qnnpack
with-proxy ./scripts/build-local.sh
./build/local/hardsigmoid-test
```
Imported from OSS
Differential Revision: D21057153
fbshipit-source-id: 31ce09643959b159a82e7083fc11e1e5e98c49ce
