Parallel Update System
Parallel update system is responsible for updating active entities in parallel.
System loops through all active entities in parallel. For each entity
updateParallel callback is executed.
If a truthy value is returned, the entity is marked as to be despawned.
Due to the parallel nature of sequential update system, it is recommended to put majority of the workload of each entity into
updateParallel callback. For example, calculate entity position and draw skin sprites.