Add rerank

[jperez999]

Description

Adds reranker to be used in batch example. Also fixed recall to work with the retriever object to get queries.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.
• If adjusting docker-compose.yaml environment variables have you ensured those are mimicked in the Helm values.yaml file.

[jioffe502]

The default here is the model name, which means any code that creates a Retriever() without explicitly setting reranker will download and load the 1B model. The docstring on line 58 says "Set to None to skip reranking (default)"

should this default to None instead so reranking is opt-in?

The batch_pipeline.py handles this correctly with the --reranker bool flag

this is just about the dataclass default for direct Retriever() callers.