Add query expansion for hybrid/hyde search

[Enniwhere]

Description:
We want to be able to use query expansion to extract multiple targeted queries when doing hybrid/hyde search.

Acceptance criteria:

• Ability to extract a number of keyword queries from a given user query, capped by a fixed number (max n).
• Ability to extract a number of hyde queries from a given user query, capped by a fixed number (max m).
• Ability to do batch search in the database.

Technical details:
Optional technical details for context.

Design:
Optional details on design for context.