[BUG] OCItemTracker never returns OCCore

Just noted OCItemTracker requests an instance of OCCore from OCCoreManager, but doesn't return it.

This shouldn't really matter if the shortcuts appex is only short-lived and terminated after running the tasks.

If the appex is kept alive by the Shortcuts app, I'd like to propose returning the core to the OCCoreManager 10 seconds after an action has Shortcuts action has completed.

Why 10 seconds? To open a time window within which the running OCCore can be "re-used" by the next shortcuts action without the overhead and delay of starting a new instance - but also to make sure it's properly terminated eventually.

To implement this, OCItemTracker could

• return a taskCompletionHandler to the completionHandler, which the action using OCItemTracker could call when it has completed its task.
• return the OCCore to OCCoreManager from within the taskCompletionHandler that was called by the action after finishing.

Start by tracing how OCItemTracker requests OCCore from OCCoreManager and how Shortcuts actions signal completion. Check the actions using OCItemTracker to understand the proposed taskCompletionHandler flow. Done means the core can be reused for 10 seconds after completion and is then returned to OCCoreManager.