Can we move the SPI definition in config-center-api to dubbo-common?

I am thinking of moving the SPI definition in `config-center-api` to `dubbo-common`. The `DynamicConfiguration`, which works as a basis for almost features that need configuration inputs, can help us to get properties from external config center. Putting it in the code base module would be more convenient for other modules that rely on it to use, and also helps to simplify the dependency structure.