A suggestion for isolating config data and governor rules with Apollo config server

- [x] I have searched the [issues](https://github.com/apache/dubbo/issues) of this repository and believe that this is not a duplicate.
- [x] 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: 2.7.3
* Operating System version: macOS10.12.6
* Java version: 1.8

有个问题 现在把动态配置和服务治理规则都放到一个统一的namespace（dubbo）下，但是启动的时候会去把该namespace的数据都加载过来，这对于大量服务启动来说，会产生不小的压力。

Start by tracing Dubbo 2.7.3 startup handling for Apollo's unified `dubbo` namespace, focusing on how dynamic configuration and service-governance rules are loaded. Clarify the intended separation of these data types, then verify that startup no longer loads unnecessary configuration for large numbers of services.

Written by the indexing model from the issue text.