refactors and big improvements

Changes

Moved some tickers and listeners to AlienManger and WorldManager. cleaned up some stuff.

[ ] I have fully tested the proposed changes and promise that they will not break world generation, mob spawning, and the like.
[ ] I followed the existing code standards and didn't mess up the formatting.
[ ] I did my best to add documentation to any public classes or methods I added.
[ ] I have added Nonnull and Nullable annotations to my methods to indicate their behaviour for null values