[parameter](query timeout) change default query timeout to 15min (#24480)

Co-authored-by: yiguolei <yiguolei@gmail.com>

fe/fe-core/src/main/java/org/apache/doris/qe/SessionVariable.java

@@ -451,7 +451,7 @@ public class SessionVariable implements Serializable, Writable {
 
     // query timeout in second.
     @VariableMgr.VarAttr(name = QUERY_TIMEOUT)
-    public int queryTimeoutS = 300;
+    public int queryTimeoutS = 900;
 
     // The global max_execution_time value provides the default for the session value for new connections.
     // The session value applies to SELECT executions executed within the session that include