feat: reranking backend integrated in with RAG

[CollectiveUnicorn]

Type: Feature

Description: Enhance the API to include reranking as an option when RAG is performed, to improve the quality of the RAG output.

User Story:
As an API user, have thee RAG results reranked to increase the quality of the results.

Acceptance Criteria:

• Results from the Runs endpoint that utilize RAG will use reranking if it is enabled.
• There is a way to configure whether or not reranking will be used in the results.
• The leapfrogai query endpoint should use reranking if it is enabled.