### Environment

* Dubbo version: dubbo-registry-nacos 2.7.6
* Operating System version: Win10
* Java version: JAVA 8

### Steps to reproduce this issue
1 springboot  yml配置如下： 
registry:
     address: nacos://127.0.0.1:8848
     simplified: true
     group: dubbo-local
  metadata-report:
            address: nacos://127.0.0.1:8848
            group: dubbo-local

2 登陆nacos 1.2.1 控制台发现元数据 group配置生效，但是服务管理下的group依旧是DEFAULT_GROUP。

3 跟了下dubbo-registry-nacos 2.7.6的代码 发现在调用NamingService中 没有传入配置的group参数，使用的默认组参数 
 public void doRegister(URL url) {
        String serviceName = this.getServiceName(url);
        Instance instance = this.createInstance(url);
        this.execute((namingService) -> {
            namingService.registerInstance(serviceName, instance);
        });
    }

Pls. provide [GitHub address] to reproduce this issue.

### Expected Result

What do you expected from the above steps？

### Actual Result

What actually happens?

If there is an exception, please attach the exception trace:

```
Just put your stack trace here!
```

/**
     * All supported categories
     */
    private static final List<String> ALL_SUPPORTED_CATEGORIES = Arrays.asList(
            PROVIDERS_CATEGORY,
            CONSUMERS_CATEGORY,
            ROUTERS_CATEGORY,
            CONFIGURATORS_CATEGORY
    );
    private static final int CATEGORY_INDEX = 0;
    private static final int SERVICE_INTERFACE_INDEX = 1;
    private static final int SERVICE_VERSION_INDEX = 2;
    private static final int SERVICE_GROUP_INDEX = 3;
    private static final String WILDCARD = "*";
    /**
     * The separator for service name
     * Change a constant to be configurable, it's designed for Windows file name that is compatible with old
     * Nacos binary release(< 0.6.1)
     */
    private static final String SERVICE_NAME_SEPARATOR = System.getProperty("nacos.service.name.separator", ":");
    /**
     * The pagination size of query for Nacos service names(only for Dubbo-OPS)
     */
    private static final int PAGINATION_SIZE = Integer.getInteger("nacos.service.names.pagination.size", 100);
    /**
     * The interval in second of lookup Nacos service names(only for Dubbo-OPS)
     */