Set a new custom update order of all engine systems in Unity.
This method changes the update order of Unity to the one specified. Only the systems you include in the new player loop will run. If you omit any systems, they will not run at all. You can insert custom script entry points in the update order before setting it. For example, this allows you to add a script which runs right before physics or in other places where scripts are not run by default. The new update order will not take effect until the next full player loop iteration, but the changes will be immediately visible in subsequent calls to GetCurrentPlayerLoop.