Add AVX-512 implementation for the distance and scalar quantizer functions. (facebookresearch#3853)

Summary:
The distance and scalar quantizer functions currently have AVX2 implementations. This patch adds the AVX-512 equivalents for each of the AVX2 implementations.

While preparing to push this PR, I realized that you have already implemented the AVX-512 equivalent for [HNSW::MinimaxHeap::pop_min](https://github.com/facebookresearch/faiss/blob/a166e13a25b2a5fe46adce4d7d06677d5199e598/faiss/impl/HNSW.cpp#L1176-L1265), which is great.

Pull Request resolved: facebookresearch#3853

Test Plan:
Imported from GitHub, without a `Test Plan:` line.

Top of the stack D62993711 is green

Reviewed By: asadoughi

Differential Revision: D62989543

Pulled By: mengdilin

fbshipit-source-id: 913403fadbfc512d195fe3411ee761d8ad025245

Author: mulugetam