pruneStaleEntries
Deletes cache entries that no schematic currently maps to.
Entries are keyed by schematic contents, Minecraft data version and WorldEdit version, so updating any of the three leaves the previous generation of entries behind — as does deleting a content pack. Without this, the cache folder keeps a full copy of every schematic set the server has ever run.
Parameters
schematicFiles
every schematic file this folder's loader currently owns, not just the ones read this pass — anything unaccounted for is deleted
cancellationCheck
run between files; may abort the prune by throwing