Dubbo 3 supports Thin SDK

Based on Dubbo 3.0 to slim Dubbo, only retain the core RPC capabilities, consider the capabilities that Service Mesh can provide natively, and strip the existing governance capabilities to enable Dubbo to access Sidecar in a lighter way, with the help of Sidecar (Envoy, Mosn) Governance capabilities.

Project requirements:
- Dubbo 3 supports independent packaging as Thin SDK mode
- Dubbo 3 supports non-registration-aware calls
- Instructions for use and use cases based on the Istio governance system

Skills requirement:
- Proficiency in Java
- Familiar with Service Mesh
- Familiar with cloud native middleware such as Istio, Envoy, Mosn

基于 Dubbo 3.0 对 Dubbo 进行瘦身，仅保留核心 RPC 能力，考虑 Service Mesh 所能原生提供的能力，剥离现有的治理能力使 Dubbo 以一个更轻量化的方式接入 Sidecar，借助 Sidecar（Envoy、Mosn）的治理能力。

产出要求：
- Dubbo 3 支持独立打包为 Thin SDK 模式
- Dubbo 3 支持无注册中心感知调用
- 使用说明文档以及基于 Istio 治理体系的用例

技术要求：
- 熟练使用 Java
- 熟悉 Service Mesh
- 熟悉 Istio、Envoy、Mosn 等云原生中间件