On each tick, Paper runs EntityScheduler's executeTick of each entity. This is a bit expensive, due to ArrayDeque's size() call because it ain't a simple "get the current queue size" function, and due to the thread checks.
To avoid the hefty ArrayDeque's size() call, we check if we *really* need to execute the executeTick, by checking if currentlyExecuting is not empty or if oneTimeDelayed is not empty.
Most entities won't have any scheduled tasks, so this is a nice performance bonus. These optimizations, however, wouldn't work in a Folia environment, but because in SparklyPaper executeTick is always executed on the main thread, it ain't an issue for us (yay).
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
