Complete the seperation of the search functionality from the federation component

[sh-ura]

A user wants to search the Katsu metadata service and the Bento Variant service simultaneously with a query like individual disease = D AND variant = V.
As a developer, I want to support users performing these searches without federating the searches. Federation is not necessary for my prototype, and I would like to be able to work with Bento's cross-service search functionality without being confused by federation-specific documentation that does not apply to my use-case.

Acceptance Criteria

• User is able to simultaneously search a single site's Katsu and Variant services with a single query
• Developer is able to support searches across Bento services using chord_singularity, without there being any dependency on the federation of searches across sites/instances of Bento
• Documentation about the Bento Search and Federation services are clear on how to quick start each of them, at least using chord_singularity
• Documentation about the Bento Search and Federation services are clear on which configurations and parameters in the docs apply to which service

Resources

@davidlougheed has done all of the refactoring needed to split the search and federation functionalities, but the final severing remains to be done. David can be consulted for the details on what is ready to go and what needs additional work.