Separate exercise events, add additional metadata

[trestletech]

• Renamed the exercise_submission event to exercise_result and added the following fields:

  1. id - a randombly generated identifier that can be used to align with the associated exercise_result event.
  2. time_elapsed - the time required to run the exercise (in seconds)
  3. timeout_exceeded - indicates whether the exercise was interrupted due to an exceeded timeout. May be NA for some platforms/evaluators if that information is not known or reported.

• Added an exercise_submitted event which is fired before evaluating an exercise. This event can be associated with an exercise_result event using the randomly generated id included in the data of both events.