Struct PollPendingPathsSystem Extends ISystem

Checks if paths have been calculated, and updates the agent's paths if they have.

This is essentially a replacement for Path.callback for ECS agents.

This system is a bit different in that it doesn't run in the normal update loop, but instead it will run when the AstarPath.OnPathsCalculated event fires. This is to avoid having to call a separate callback for every agent, since that would result in excessive overhead as it would have to synchronize with the ECS world on every such call.