hardswish: make it work in static quantization (#36545)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/36545
* adds a quantized nn.module for Hardswish so we can observe activation values
* modifies the hardswish op to allow specifying scale + zero_point
* makes hardswish model be properly swapped in static quantization
Test Plan:
added tests and they pass for:
* the new _out flavor of hardswish
* QNNPACK changes
* static quant e2e
Imported from OSS
Differential Revision: D21045320
fbshipit-source-id: ab7e52f0f54a7d5923ab6f58197022cc28c12354
