The new implementation of pre-gen is currently still missing a system to freeze entitied. That means, all entities should generally have NoAI after they are loaded, and chicken timers need to be taken care of separately.

Because of performance considerations, only newly created chunks should be processed. Since chunk genetation is asynchronous, there needs to be a second pass which behaves the same way as the concept for loading chunks, but first checks the chunk being loaded, and then processes entities.

At the start of the game, entities need to be unfrozen again.