xDS protocol implementation status

I noticed that Dubbo has an implementation of xDS protocol available in [`v3.0.5`](https://github.com/apache/dubbo/tree/dubbo-3.0.5/dubbo-registry) but it isn't in [`master`](https://github.com/apache/dubbo/tree/master/dubbo-registry) or [`3.0.0`](https://github.com/apache/dubbo/tree/3.0/dubbo-registry) branches. Are this feature read to use in production (along with Istio on any other xDS control plane) or it wasn't officially release yet?

If this feature was released, is there any example about how to use Dubbo's xDS?

Compare the dubbo-registry directories in the v3.0.5, master, and 3.0 branches referenced in the issue. First establish whether the xDS implementation is available and supported, then look for an existing usage example; done means the production-readiness status and a verified Dubbo xDS example are documented.

Written by the indexing model from the issue text.