Changelog:

  Added halfvec type
  Added sparsevec type
  Added support for indexing bit type
  Added support for indexing L1 distance with HNSW
  Added binary_quantize function
  Added hamming_distance function
  Added jaccard_distance function
  Added l2_normalize function
  Added subvector function
  Added concatenate operator for vectors
  Added CPU dispatching for distance functions on Linux x86-64
  Updated comparison operators to support vectors with different dimensions