Feat: New indexer management API for querying unclaimed query fees

[datanexus-vincent]

Now that query fees are a bigger part of the equation when thinking about reallocations, it would be nice to expose unclaimed query fee data in the indexer management API so that tools like Indexer Tools can easily query and display this data.

Just a simple unclaimedFees schema mapping allocation IDs and unclaimed query fees with the ability to query by allocation ID would be sufficient for the use case I'm thinking of.