Consolidate EmbeddingMetadataStorage into VectorDB

[kyle65463]

#69

What was done

• Removed separate EmbeddingMetadataStorage and EmbeddingStore classes and consolidated metadata management directly into vector database implementations
• Refactored vector database interface to handle both embeddings and their associated metadata
  • Updated VectorDB.add() method to accept EmbeddingMetadataObj parameter
  • Added metadata management methods: get_metadata(), update_metadata(), and get_all_embedding_metadata_objects()
• Updated all tests, benchmarks, integration tests and codebase to use the new unified vector database interface that manages both embeddings and metadata
• Removed ChromaVectorDB and FAISSVectorDB implementations, keeping only HNSWLibVectorDB for now

Notes

• Only HNSWLibVectorDB is included in this PR - I will add other vector database implementations in future PRs to ensure this architectural change works correctly with the existing implementation first.