Pre-Retrieval:
* Consolidated naming and documentation
Retrieval:
* Consolidated naming and documentation
* Introduced DocumentJoiner sub-module and CompositionDocumentJoiner operator
Post-Retrieval:
* Introduced main interfaces for sub-modules. Implementation waiting for missing features in Document APIs
Orchestration:
* Introduced QueryRouter sub-module and AllDocumentRetrieversQueryRouter operator
Generation:
* Consolidated naming and documentation
Advisor:
* Introduced BaseAdvisor to reduce boilerplate when implementing Advisors
* Extended RetrievalAugmentationAdvisor to include the new sub-modules
Relates to #gh-1603