Change min_refreshed_at to min_updated_at in gateway_info_v2

[kurotych]

Related PR: helium/oracles#910

[dcyoung]

@kurotych i noticed the v2 endpoint only applies to the stream endpoint. Should the info or info_batch endpoints get a v2 as well?

[jeffgrunewald]

may be out of scope for the immediate issue @kurotych is working on but i would tend to agree that we should update the gateway service to provide v2 implementations of the info and info batch rpcs since they won't otherwise have a mechanism for accessing the gateway info for a single hotspot or subset of the entire fleet that includes the new metadata from the chain.

the impl for the info_batch is the same as for the stream (they both return a stream of gateway info messages) but that one just passes the list of hotspot addresses as a filter to the database query

[kurotych]

I agree. I will start work on it in the current PRs.

@dcyoung @jeffgrunewald