Add sanity tests for Global IO framework and provide a hook for QE tests to read the results.

Please refer to MB-10849 for background on this ticket.
Add sanity checks for the following cases:
1)Verify that high priority bucket tasks get enqueued only in high priority task queues and similarly for low priority bucket tasks.
2)Verify logic such as "maxWorkers per Task Type". I would need to make sure all other task queues are empty except for a particular task set such as writes and that the number of threads servicing the write task queue does not exceed the setting.
3)Verify that among multiple tasks in the ready queue, the tasks are ordered by priority.
4)Verify that when a delete bucket command is received, the already enqueued tasks are executed prior to deletion of the bucket.
5)Verify a task is enqueued but not executed yet if another updated task for the same task is received, the first task is marked as dead.