Replace faiss bfKnn with code that leverages our pairwise_distance api
and select_k api - by computing tiling over the inputs.

This lets us remove faiss as a dependency

This reverts commit 8eaba84.

Change didn't seem to build in CI

Also remove metrics processors - since is handled inside PW distance

This reverts commit fe728e9.

This is causing incorrect results, just use the faiss select_k call
instead

…4-bfknn