Adds nullability annotations for all methods
Fixes some nullability problems and inconsistencies
Gets rid of RelativeBlockVector's inner class
Changes RelativeBlockVector to a record
Simplifies FromTheEndTeleportation's storage, and makes it into a minimal record
Removes the putStringInList method
Gets rid of some primitive list usage
Fixes some incorrect method accessibility
Removes some redundancy in PortalOption
Adds all chunk unloading to a queue
Adds a thread which unloads chunks
Updates chunk unload requests such that a chunk won't be unloaded twice,
and an old unloading request cannot unload a chunk too soon
