Promote vector similarity index to beta

Why it matters

This feature allows users to leverage vector similarity indexes for efficient similarity searches and nearest neighbor queries over vector data. By promoting it to beta and requiring explicit enabling, ClickHouse ensures stability and controlled adoption while providing enhanced capabilities for vector-based data retrieval.

How to use it

To use the vector similarity index, set the alias setting enable_vector_similarity_index to 1. This enables the feature and allows creation and utilization of vector similarity indexes in your queries.