fix: PromisePoolCluster.of returns PromisePoolCluster instead of PoolNamespace (#3091)

Author: jcmartineztiempo

test/esm/integration/pool-cluster/test-promise-wrapper.test.mjs

@@ -86,21 +86,25 @@ const { createPoolCluster } = require('../../../../promise.js');
 
     const poolNamespace = poolCluster.of('MASTER');
 
+    assert.equal(poolNamespace.poolNamespace, poolCluster.poolCluster.of('MASTER'));
+
     const connection = await poolNamespace.getConnection();
 
     assert.ok(connection, 'should get connection');
     connection.release();
 
-    const result = await poolNamespace.query(
-      'SELECT 1 as a from dual where 1 = ?',
+    const [result] = await poolNamespace.query(
+      'SELECT 1 as a where 1 = ?',
       [1],
     );
     assert.equal(result[0]['a'], 1, 'should query successfully');
 
-    const result2 = await poolNamespace.execute(
-      'SELECT 1 as a from dual where 1 = ?',
+    const [result2] = await poolNamespace.execute(
+      'SELECT 1 as a where 1 = ?',
       [1],
     );
     assert.equal(result2[0]['a'], 1, 'should execute successfully');
+
+    poolCluster.end();
   });
 })();