A utility for generating worlds asynchronously should be added

[haykam821]

Because vanilla world generation is unfortunately too slow for our purposes, it will block the server thread and give the appearance of the server freezing to other players, who may be playing another game. As a result, a feature was added to Item Hunt in NucleoidMC/ItemHunt@1c9e7e8 where players would wait in a void world while the main world generated.

Since vanilla world generation is used in other games, such as Beacon Breakers, Death Swap, and UHC, having a common utility to generate worlds asynchronously and place players into a void world during world generation would be useful.