Executor
This is a simple executor. There is a single Arc<Executor> type that can be shared between many worker threads.
Each worker will continuously run executor.poll_once() which will
- Pop a task from the shared task queue
- Parking the thread if no tasks are available
- Poll that task
The task will be polled with a context that will reference that task (using a Mutex<Option<Task>>),
and a copy of the executor.
Calling wake on this context will then call executor.wake(task). If there are threads sleeping, one will be woken up.