Try Annoy instead of HNSW

[sanikolaev]

We recently added HNSW support for KNN to this library. Together with Manticore Search it works so - https://manual.manticoresearch.com/dev/Searching/KNN#K-nearest-neighbor-search

It would be great to implement, test and bechmark https://github.com/spotify/annoy vs the integrated hnsw library in the context of Manticore Search.