KVStore tracking data over time

[czarcas7ic]

Right now, we see our pruned snapshots slowly increasing in size. Maybe a few months ago they were 15GB and now are around 19GB. We really have no idea what module the space is coming from. I think it would be a really useful ability to have insight into space per module, and see which modules are growing over the time period. This could result in storage performance improvements if we can find where to look. Even better would be a subcategorization by KVStore Key