add faiss ivf index feature

[MXueguang]

It's good to add ivf feature here https://github.com/castorini/pyserini/blob/master/pyserini/index/faiss.py

ref comments from @t-k- : https://github.com/castorini/pyserini/issues/798#issuecomment-944807307 we also need to think about the way to split the index during index time.