aten.hardshrink.default in unary_ops (#3681)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/3681

Implement aten.hardshrink in unary_ops
```
func: hardshrink.out(Tensor self, Scalar lambd=0.5, *, Tensor(a!) out) -> Tensor(a!)
```

Another standalone implementation can be found: D57500203

Reviewed By: SS-JIA

Differential Revision: D57573208

fbshipit-source-id: 7939543fddf8e39f6bb4e681c43d386140ae560b