builtins,workloadindexrec: Add fingerprint id to workload_index_recs builtin

Adds another column to the workload_index_recs builtin that contains an
array of fingerprint ids that the recommended indexes were originally
recommended for.

Resolves: #141947
Epic: CRDB-42980
Release note (sql change): Changes the return type of the workload_index_recs builtin
to be two columns. The first column, "index_rec", remains a string type that
contains the index recommndation. The second column, "fingerprint_ids", is
new and has the "byte[]" type.

Author: kyle-a-wong

docs/generated/sql/functions.md

@@ -1554,9 +1554,9 @@ the locality flag on node startup. Returns an error if no region is set.</p>
 </span></td><td>Immutable</td></tr>
 <tr><td><a name="unnest"></a><code>unnest(input: anyelement[]) &rarr; anyelement</code></td><td><span class="funcdesc"><p>Returns the input array as a set of rows</p>
 </span></td><td>Immutable</td></tr>
-<tr><td><a name="workload_index_recs"></a><code>workload_index_recs() &rarr; <a href="string.html">string</a></code></td><td><span class="funcdesc"><p>Returns set of index recommendations</p>
+<tr><td><a name="workload_index_recs"></a><code>workload_index_recs() &rarr; tuple{string AS index_rec, bytes[] AS fingerprint_ids}</code></td><td><span class="funcdesc"><p>Returns index recommendations and the fingerprint ids that the indexes will impact</p>
 </span></td><td>Immutable</td></tr>
-<tr><td><a name="workload_index_recs"></a><code>workload_index_recs(timestamptz: <a href="timestamp.html">timestamptz</a>) &rarr; <a href="string.html">string</a></code></td><td><span class="funcdesc"><p>Returns set of index recommendations</p>
+<tr><td><a name="workload_index_recs"></a><code>workload_index_recs(timestamptz: <a href="timestamp.html">timestamptz</a>) &rarr; tuple{string AS index_rec, bytes[] AS fingerprint_ids}</code></td><td><span class="funcdesc"><p>Returns index recommendations and the fingerprint ids that the indexes will impact</p>
 </span></td><td>Immutable</td></tr></tbody>
 </table>