Feature request: Support zvec as vector backend

[ccdv-ai]

zvec is very fast for dense and sparse retrieval.
Here some benchmarks.

[davidmezzetti]

I saw this one. I was interested to see benchmarks vs things like Faiss and Hnswlib before integrating. I believe they intend to do that.

[davidmezzetti]

Probably also would need to wait for this: alibaba/zvec#23

[davidmezzetti]

Also put this issue out there alibaba/zvec#159. Hopefully we get more relevant benchmarks (i.e. Faiss, Hnswlib).