disable regrade if a teacher removes an answer for a question after submissions are made

fixes CNVS-9853

test plan:
  as a teacher
    - create a quiz with a multiple choice answer
    - publish the quiz

  as a student
    - take the quiz

  as a teacher
  variation 1:
    - remove one of the answers from the multiple choice question
    - you should receive an alert telling you that regrade will disable for the question
    - confirm deleting the question
    - attempt to change the answer. The regrade box should not allow you to regrade
    - change the answer and save the quiz
    - edit the quiz again
    - once again attempt to change the answer for the question. Regrade should still be disabled

  variation 2:
    - remove one of the answers from the multiple choice question
    - you should receive an alert telling you that regrade is no disabled for the question
    - confirm deleting the question
    - don't change any answers.
    - save the quiz
    - edit the quiz again
    - attempt to change the answer for the question. Regrade should still be disabled

  variation 3:
    - attempt to change the answer. The regrade box should allow you to regrade
    - choose a regrade option (but don't update the question)
    - remove one of the answers from the multiple choice question
    - you should receive an alert telling you that regrade will disable for the question
    - confirm deleting the question
    - the regrade box should now say that the regrade is disabled
    - edit the quiz again
    - once again attempt to change the answer for the question. Regrade should still be disabled

  variation 4:
    - attempt to change the answer. The regrade box should allow you to regrade
    - choose a regrade option and save the quiz
    - regrade should be performed successfully

  other things to check:
    - various changes with the general idea that regrade should disable if you delete questions
    - copying quiz to a different course (regrade should re-enable when copied)
    - multiple submissions for a quiz (regrade should remain disabled)

Change-Id: Ic697e51519ce995a29064ef49b3384992a228b0b
Reviewed-on: https://gerrit.instructure.com/27838
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Reviewed-by: Jason Madsen <jmadsen@instructure.com>
Product-Review: Derek DeVries <ddevries@instructure.com>