- [x] I have searched the [issues](https://github.com/apache/dubbo/issues) of this repository and believe that this is not a duplicate.
- [x] I have checked the [FAQ](https://github.com/apache/dubbo/blob/master/FAQ.md) of this repository and believe that this is not a duplicate.

### Environment

* Dubbo version: 3.0.0
* Operating System version: Mac OS Big Sur 11.4
* Java version: 1.8

### Steps to reproduce this issue

1. 克隆dubbo代码，检出3.0版本的tag；
2. 修改demo工程，制造1个rest协议报错的case；
3. 启动demo工程 /dubbo-demo/dubbo-demo-xml/dubbo-demo-xml-provider；
4. 观察控制台日志，发现有部分错误日志被打印到了StdError，截图如下：

![image](https://user-images.githubusercontent.com/22830937/122713904-058eb580-d299-11eb-935e-4080d6ab6e00.png)

### Expected Result

将错误日志桥接到Dubbo自己的日志系统，而非打印到StdError。

### Actual Result

错误日志打印到了StdError，导致基于Dubbo日志做的收集和其它扩展失效。

关键代码：

1. 类文件： ``org.apache.dubbo.remoting.http.jetty.JettyHttpServer``；
2. 代码位置：第33行 ``Log.setLog(new StdErrLog());``。
ServletHolder servletHolder = servletHandler.addServletWithMapping(DispatcherServlet.class, "/*");
        servletHolder.setInitOrder(2);
        
        
        
        ServletContextHandler context = new ServletContextHandler(server, "/", ServletContextHandler.SESSIONS);
        context.setServletHandler(servletHandler);
        ServletManager.getInstance().addServletContext(url.getParameter(Constants.BIND_PORT_KEY, url.getPort()), context.getServletContext());
        try {
            server.start();
        } catch (Exception e) {
            throw new IllegalStateException("Failed to start jetty server on " + url.getParameter(Constants.BIND_IP_KEY) + ":" + url.getParameter(Constants.BIND_PORT_KEY) + ", cause: "
                    + e.getMessage(), e);
        }
    }
    @Override
    public void close() {
        super.close();
        
        ServletManager.getInstance().removeServletContext(url.getParameter(Constants.BIND_PORT_KEY, url.getPort()));
        if (server != null) {
            try {
                server.stop();
            } catch (Exception e) {
                logger.warn(e.getMessage(), e);
            }
        }
    }
}