Dynamically determine metadata read indices based upon query range

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While the rotation interval of the ES write index—in other words, how frequently Heroic consumers stop writing to an elasticsearch index, create a new one and start writing to it instead—is configurable, the maximum number of read indices is not configurable and not dynamic.

maxReadIndices should be dynamically determined based upon the date range of a query and the rotation interval of Elasticsearch indices. We can then narrow the metadata response to only return documents relevant to the query as opposed to all documents. This will narrow the query to BigTable and lay the groundwork for future guardrails to enable malleable series limits that take query range into consideration.