%task status etc should add affected tasks to task engine for continued monitoring

[BoPeng]

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Currently, when we open a notebook with a bunch of tasks, and refresh, it will get the most recent status but the tasks are not monitored so manual update will be needed. It makes sense to add the tasks to task engine for continuous monitoring.

[BoPeng]

One of the problems is that we have been refraining from monitoring too many tasks because because sos status can be an expensive operation and sending too much information for the frontend can also be problematic. If a task is completed, we have stopped checking its status. However, nothing stops the user from running sos execute task_id -s force from command line and it is arguable if the frontend should be notified since the command is executed outside of the notebook session.