adds quantized implementation of hard sigmoid (#34607)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/34607
Adds quantized version of hardsigmoid activation.
Note: not implementing the _ and .out versions is
currently intended, because the implementation changes the scale and
zp and it's nice to not allow the user to specify scale
and zp. Lmk if we should handle this differently.
Test Plan:
tests
benchmarks
Imported from OSS
Differential Revision: D20480546
fbshipit-source-id: 9febcb44afd920125ed2ca4900492f0b712078ea
