Dubbo能提供一个扩展去支持用户在发现提供者实例变化时进行一些操作吗

如提供一个ProviderChangeListener(oldUrls,newUrls)这样的接口

Start by locating the provider-discovery path where instance changes are detected. Determine how an extension could receive the old and new provider URL sets, then define callback timing, lifecycle, and behavior for additions and removals. Add coverage for provider changes and verify the listener is invoked with the expected values.

Written by the indexing model from the issue text.