Add listener support for context entry evaluation

From Simon:
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We are starting to have a lot of clients asking for the ability to see the result of boxed context rows inside.

Right now, we have only the result being returned (and if there is no return, we get the context).

We already are hook on the DMNRuntimeEventListener for afterEvaluateDecisionTable, would it be possible to have another method added on that listener that would notify when a context entry was evaluated with the result?