chore: use describe_indices for index inspection

[ddupg]

Summary

• Replace deprecated list_indices() calls with describe_indices().
• Update tests, examples, and docs to use IndexDescription fields.

Why

list_indices() is deprecated and can emit warning logs during index workflows. Since lance-ray already depends on pylance>=8.0.0b11, these call sites can use describe_indices() directly.

Testing

• ruff check lance_ray/index.py lance_ray/search.py tests/test_distributed_indexing.py tests/test_distributed_search.py tests/test_vector_index_options.py examples/distribute_fts_index.py
• python -m pytest -o addopts='' tests/test_vector_index_options.py tests/test_distributed_indexing.py tests/test_distributed_search.py -k "index or optimize_indices or select_vector_index" -vv -s

[github-actions]

ACTION NEEDED
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