[quant] Create PerRowQuantizer for floating point scale and zero_point (#42612)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/42612
Add a new Quantizer that supports an input zero point (bias) that can be float.
The quantization equation in this case is
Xq = (Xf - bias) * inv_scale, where bias is float zero_point value
We start with per-row implementation and can extend to per-tensor in the future, if necessary
Test Plan:
python test/test_quantization.py TestQuantizedTensor
Imported from OSS
Reviewed By: jerryzh168
Differential Revision: D22960142
fbshipit-source-id: ca9ab6c5b45115d3dcb1c4358897093594313706
