Optimizes "image in map" maps, without requiring the map to be locked, which some old map plugins may not do
This has the disadvantage that the vanilla map data will never be updated while the CraftMapRenderer is not present, but that's not a huuuge problem for us
The "distanceToSqr" call is a bit expensive, so avoiding it is pretty nice, around ~15% calls are skipped with this check
We could also check if the x,y,z coordinates are equal, but for now, let's just keep the identity check, which also helps us since Minecraft's code does reuse the original delta movement Vec3 object
The single thread per world is actually better because now we can profile each world separately. We still mimick the original thread pool by using a semaphore, this way we don't end up saturating all cores
