Add IVF_PQ backwards compatibility data generation and testing

[jparismorgan]

What

Add IVF_PQ backwards compatibility data generation and testing.

Testing

Can generate:

(TileDB-Vector-Search-3) ~/repo/TileDB-Vector-Search-3 python backwards-compatibility-data/generate_data.py 0.20.0
/opt/homebrew/anaconda3/envs/TileDB-Vector-Search-3/lib/python3.9/site-packages/tiledb/vector_search/ivf_pq_index.py:198: UserWarning: The IVF PQ index is not yet supported, please use with caution.
  warnings.warn("The IVF PQ index is not yet supported, please use with caution.")
/opt/homebrew/anaconda3/envs/TileDB-Vector-Search-3/lib/python3.9/site-packages/tiledb/vector_search/ivf_pq_index.py:149: UserWarning: The IVF PQ index is not yet supported, please use with caution.
  warnings.warn("The IVF PQ index is not yet supported, please use with caution.")
false

And python tests pass:

(TileDB-Vector-Search-3) ~/repo/TileDB-Vector-Search-3 pytest apis/python/test/test_backwards_compatibility.py -s                  

============================================= test session starts =============================================
platform darwin -- Python 3.9.18, pytest-7.4.3, pluggy-1.3.0
rootdir: /Users/parismorgan/repo/TileDB-Vector-Search-3
collected 1 item                                                                                              

apis/python/test/test_backwards_compatibility.py .

============================================== warnings summary ===============================================
apis/python/test/test_backwards_compatibility.py::test_query_old_indices
  /opt/homebrew/anaconda3/envs/TileDB-Vector-Search-3/lib/python3.9/site-packages/tiledb/vector_search/ivf_pq_index.py:149: UserWarning: The IVF PQ index is not yet supported, please use with caution.
    warnings.warn("The IVF PQ index is not yet supported, please use with caution.")

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
======================================== 1 passed, 1 warning in 1.65s =========================================

And C++ tests pass.