CMC thread dump

[wingzero54]

Paper dumped a CMC thread that caused a massive server lag spike, ChunkMetaManager https://pastebin.com/dQU3HSaZ

[Maxopoly]

This is because it can't acquire a lock on the unloading queue, while it is being flushed. Could fix it architecturally or just lower the timer to reduce the symptoms.

#103 attempts to address it, but was never fixed