Per Channel quantization APIs (#24935)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/24935
Adding per channel qtensor creation APIs
Added two tests:
EmptyPerchannelQuantized in aten/src/ATen/test/quantized_test.cpp
test_perchannel_qtensor_creation in test/test_quantized_tensor.py
ghstack-source-id: 88888140
Test Plan: buck test mode/dev caffe2/test:quantized -- 'test_per_channel_qtensor_creation' --print-passing-details
Differential Revision: D16696959
fbshipit-source-id: f179247cc1c461bec215e17b51263060003493a5
