Fixes & improvements

• Updated the pgvector extension to version 0.4.4. If you installed this extension previously and want to upgrade to the latest version, please refer to Update an extension version for instructions.
• Added a check for available memory when creating an Hierarchical Navigable Small World (HNSW) index using the pg_embedding extension. HNSW builds indexes in memory. Insufficient memory for the index size could result in out-of-memory errors.