Attaches the scheduler to the calling context. After this method returns, the calling context is managed by the scheduler and the scheduler becomes the current scheduler.
Attaching a scheduler implicitly places a reference on the scheduler.
At some point in the future, you must call the CurrentScheduler::Detach method 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.
This method will throw an improper_scheduler_attach exception if this scheduler is the current scheduler of the calling context.