hardsigmoid: add PyTorch wrapper for the QNNPACK path (#36699)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/36699
Hooks up the QNNPACK op from the previous PR to work in the
PyTorch layers.
Test Plan:
```
python test/quantization/test_quantized.py TestQuantizedOps.test_qhardsigmoid
python test/quantization/test_quantized.py TestQNNPackOps.test_qhardsigmoid
```
Imported from OSS
Differential Revision: D21057152
fbshipit-source-id: 5f2094d1db80575f7f65497f553ca329f7518175
