[New Quizzes] Feedback after quiz submission

[Estefania]

Now that New Quizzes are (finally!) being integrated into the module progression, it would be helpful to have the option to add feedback for students to see after submission.

Just like the existing Student Feedback that can be added to individual quiz questions, instructors should have the option to add general feedback for the quiz that would show on the result view (or on the quiz detail page after submission). With the RCE, this space could be used to add pointers  about materials to review, or to remind students of the next steps they need to take.