This enables us a fast reference to the entities current chunk instead
of having to look it up by hashmap lookups.
We also store counts by type to further enable other performance optimizations in later patches.
Sometimes a chunk region file is closed prematurely, resulting in a "Stream Closed" error on chunk saving.
Ultimately there is a race condition that causes it, but re-trying the save will avoid the issue.
Retry the save 5 times to try our best to avoid rollbacks due to chunk save failures.
