[Tech Request]: 单机 mo 配置 observability 需支持仅在CN上生效

### Is there an existing issue for the same tech request?

- [X] I have checked the existing issues.

### Does this tech request not affect user experience?

- [X] This tech request doesn't affect user experience.

### What would you like to be added ?

OB相关配置，单机MO运行时，支持仅配置 CN 或 TN、LOG。

### Why is this needed ?

单机部署的MO, OB 相关的配置需要同时配置在 log.toml, tn.toml, cn.toml 才能生效。

非常的难进行管理

### Additional information

_No response_