AlloyDB AI native vector search accelerator is now generally available (GA)

## Feature Feature AlloyDB AI native vector search accelerator is now generally available ([GA](https://cloud.google.com/products#product-launch-stages)). It includes the following features and improvements: * The `google_columnar_engine` extension is updated to automatically recommend data for searches, so you don't need to manually add vector columns to the table. For more information, see [Perform a vector search](https://cloud.google.com/alloydb/docs/ai/perform-vector-search#accelerate-filtered-vector-search). * The `alloydb_scann` extension is updated with new metrics for vector index creation. You can now use the [pg\_stat\_ann\_index\_creation](https://cloud.google.com/alloydb/docs/ai/tune-indexes?resource=scann#vector-index-metrics) view to see the number of rows present in a table at the time of index creation.