light calculations repeatedly looks up the same chunk while going
down on the Y access. Pass the chunk to it to skip many round trips
to the map lookup process.
while the gains arent as big since we have last access cache, it
should hopefully avoid many callstacks of depth and improve inlining,
as well as avoids entering a synchronized code block.
The avoiding of entering synchronized section is the main goal here.
Vanilla has risk of losing entities by causing them to be
removed from all chunks if they try to move into an unloaded chunk.
This pretty much means high chance this entity will be lost in this scenario.
There is another case that adding an entity to the world can fail if
the chunk isn't loaded.
Lots of the server is designed around addEntity never expecting to fail for these reasons,
nor is it really logical.
This change ensures the chunks are always loaded when entities are
added to the world, or a valid entity moves between chunks.
Hopefully will fix issues #1496 and #1434
Aikar