community[minor]: add additional support for BigQueryVectorSearch (#15904)

BigQuery vector search lets you use GoogleSQL to do semantic search,
using vector indexes for fast but approximate results, or using brute
force for exact results.

This PR:
1. Add `metadata[_job_ib]` in Document returned by any similarity search
2. Add `explore_job_stats` to enable users to explore job statistics and
better the debuggability
3. Set the minimum row limit for running create vector index.

docs/docs/integrations/vectorstores/bigquery_vector_search.ipynb

@@ -324,6 +324,24 @@
     "docs = store.similarity_search_by_vector(query_vector, filter={\"len\": 6})\n",
     "print(docs)"
    ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "### Explore job satistics with BigQuery Job Id"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "job_id = \"\"  # @param {type:\"string\"}\n",
+    "# Debug and explore the job statistics with a BigQuery Job id.\n",
+    "store.explore_job_stats(job_id)"
+   ]
   }
  ],
  "metadata": {