database event decode free list

[mleku]

currently, queries repeatedly decode and decode again events that are hot in the cache, especially recent ones that are sent out in open subscriptions of current websocket connections

it would make a lot of sense to eliminate the duplication of both memory and processing required for this data by changing the event decoding library into a freelist that allows avoiding unbounded spikes of memory use and unnecessary re-decoding of the binary data in the database for events that are being heavily accessed concurrently