Multithreading and different borders

[Quenteez]

I want to suggest adding multithreading of worlds to the current project. So that each world is in its own stream or several worlds are distributed in different threads. This would increase the performance on the server.
Also a useful feature would be the implementation of different WorldBorder for different worlds (at least their size).

Here are examples of implementing multithreaded worlds.
Here are examples of the implementation of different borders.