完善 JobHandlerInvoker 的执行，记录 Job 执行日志

src/main/java/cn/iocoder/dashboard/util/date/DateUtils.java

@@ -18,4 +18,8 @@ public class DateUtils {
         return System.currentTimeMillis() > time.getTime();
     }
 
+    public static Long diff(Date endTime, Date startTime) {
+        return endTime.getTime() - startTime.getTime();
+    }
+
 }