[Feature] Allow modules to extend Dubbo application configuration

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### Search before asking

- [X] I had searched in the [issues](https://github.com/apache/dubbo/issues?q=is%3Aissue) and found no similar feature requirement.

### Apache Dubbo Component

Java SDK (apache/dubbo)

### Descriptions

Allow modules to extend Dubbo application configuration to support custom configuration in other modules.
For example, I expect to define MetricsConfig in the dubbo-metrics module and PromethusConfig in the dubbo-metrics-promethus module. And in the future, I expect to define OtlpConfig in dubbo-metrics-export-otlp.

### Related issues

[Separate the code for indicator monitoring](https://github.com/apache/dubbo/issues/14016)
[Refector Metric export](https://github.com/apache/dubbo/issues/14015)

### Are you willing to submit a pull request to fix on your own?

- [X] Yes I am willing to submit a pull request on my own!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://www.apache.org/foundation/policies/conduct)

Start by reading the Java SDK configuration architecture and the related issues #14016 and #14015. Examine how dubbo-metrics and dubbo-metrics-promethus are structured, then define the extension approach so modules can provide configurations such as MetricsConfig, PromethusConfig, and OtlpConfig. Done means custom configuration from other modules can be supported without placing every configuration in the core application configuration.

Written by the indexing model from the issue text.