Change snapshot block period from 64 to 256

Currently blocks are snapshotted every 64 blocks starting backwards from the endBlock of the mining period. While this worked in the past, the recent updates to the mining formula (specifically the cap factor) make the scripts much more intensive to run and the runtime has increased to up to 4 hours with a local archive node and probably > 24 hours using an infura archive endpoint. This has caused delays in distributions when a bug is found and scripts need to be re-run.

I propose changing the snapshot block to every 256 blocks (roughly every hour). This still is frequent enough to account for changes in liquidity and greatly improves the team ability to have a more consistent distribution time going forward