com.alibaba cluster、Directory兼容失败

- [ ] I have searched the [issues](https://github.com/apache/dubbo/issues) of this repository and believe that this is not a duplicate.
- [ ] 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: 2.7.4.1
* Operating System version: mac
* Java version: 8

### Steps to reproduce this issue

1、Cluster
```java
@Deprecated
public interface Cluster extends org.apache.dubbo.rpc.cluster.Cluster {

com.alibaba.dubbo.rpc.Invoker join(com.alibaba.dubbo.rpc.cluster.Directory directory) throws
com.alibaba.dubbo.rpc.RpcException;

@Override
default Invoker join(Directory directory) throws RpcException {
return null;
}
}
```
> join为什么返回NULL

2、Directory
```java
public interface Directory extends org.apache.dubbo.rpc.cluster.Directory {

@Override
URL getUrl();

List> list(com.alibaba.dubbo.rpc.Invocation invocation) throws com.alibaba.dubbo.rpc.RpcException;

@Override
default List> list(Invocation invocation) throws RpcException {
List> res = this.list(new com.alibaba.dubbo.rpc.Invocation.CompatibleInvocation(invocation));
return res.stream().map(i -> i.getOriginal()).collect(Collectors.toList());
}
}
```
> 缺少兼容Directory，例如`CompatibleDirectory`

我们有老项目实现了Cluster，如果改新的包，很多项目都要动，量很大，所以需要兼容老的。