Get rid of `utils/kmeans.rs`

[arrayka]

• utils/kmeans.rs: KMeans has been replaced for PQ related purposes by the faster implementation in diskann-quantization. The last user of this flow is the disk-index partitioning. It's possible that the BLAS based implementation of the diskann-providers is faster than the approach taken in diskann-quantization for full-dimensional data. To that end, we should either:
  • Audit and replace the use of KMeans in disk partitioning to use diskann-quantization and get rid of the diskann-providers implementation.
  • Upgrade the implementation in diskann-quantization to be on-par for full-dimensional data.
  • Move the implementation to diskann-disk where it's actually used.