For when we want to collect reports in memory, but not save them to store.
Extract this functionality out of awsCollector to create new
liveCollector object.
Collectors hold recent reports in memory.
When querier needs 'live' data, fetch it from collectors instead
of from the long-term store.
Send reports from collector to querier in msgpack; disable compression
on REST call, otherwise Go silently decompresses, which takes longer.
