Creates a new scheduler whose behavior is described by the _Policy parameter and attaches it to the calling context. The newly created scheduler will become the current scheduler for the calling context.
The attachment of the scheduler to the calling context implicitly places a reference count on the scheduler.
After a scheduler is created with the Create method, you must call the CurrentScheduler::Detach method at some point in the future in order to allow the scheduler to shut down.
If this method is called from a context that is already attached to a different scheduler, the existing scheduler is remembered as the previous scheduler, and the newly created scheduler becomes the current scheduler. When you call the CurrentScheduler::Detach method at a later point, the previous scheduler is restored as the current scheduler.