fix(vectorstore): Correct HNSW parameter inclusion and test assertions

[PingXie]

• Fixed inclusion of HNSW parameters (M, EF_CONSTRUCTION, EF_RUNTIME) in Redis index creation.
• Corrected test assertions to accurately reflect expected key count in Redis.
• Updated check_index_exists to properly validate HNSW index configurations.

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Fixes #<issue_number_goes_here> 🦕