Apache Dubbo GSoC2022 Proxyless Mesh support

Details xDS 官方说明 https://www.envoyproxy.io/docs/envoy/latest/api-docs/xds_protocol ● Listener Discovery Service (LDS): Returns Listener resources. Used basically as a convenient root for the gRPC client's configuration. Points to the RouteConfiguration. ● Route Discovery Service (RDS): Returns RouteConfiguration resources. Provides data used to populate the gRPC service config. Points to the Cluster. ● Cluster Discovery Service (CDS): Returns Cluster resources. Configures things like load balancing policy and load reporting. Points to the ClusterLoadAssignment. ● Endpoint Discovery Service (EDS): Returns ClusterLoadAssignment resources. Configures the set of endpoints (backend servers) to load balance across and may tell the client to drop requests. 协议基础：protobuf + gRPC 实现方案 1：使用 io.grpc 的依赖手动创建原生 gRPC 服务 实现方案 2：使用 Dubbo 3.0 的新协议 测试环境控制平面 mock Envoy 提供的 Java 实例控制平面 https://github.com/envoyproxy/java-control-plane Java 版协议支持 Envoy 提供的 Java 版控制平面 API https://search.maven.org/search?q=g:io.envoyproxy.controlplane