A function that returns volatile intervals.
Volatile intervals are intervals which may still not be finalized, and thus should not be cached. The normal
use case for this is data which is being ingested via real time ingestion, and thus which will be replaced later by
new historical segments.
Retrieve a list of which intervals are volatile.
Volatile intervals should not be cached (in the same way that partial intervals are not cached) but are
returned to the user (which partial intervals are typically not). Volatile intervals will typically abut or
overlap incomplete data because they are on the forward edge of ingestion.