avoid large vector copy when query per_channel q_params (#31040)
Summary:
The quantizer use std::vector to save per_channel scales and zero_points, but when query scales(zero_points), it requires to return tensor. These lead to use std::vector to initialize tensors and it dose cost lots of time. So I change quantizer to save per_channel scales and zero_points by using tensor directly.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/31040
Differential Revision: D19701070
Pulled By: jerryzh168
fbshipit-source-id: 9043f16c44b74dd8289b8474e540171765a7f92a
