Masquerading staff override hidden special exams [TNL-4808] (#12806)
Masquerading staff override hidden special exams [TNL-4808] (#12806)

Allows staff using "view as specific student" mode to bypass edx-proctoring
hiding special exams from students, to allow for more useful debugging.

Includes "shim" pattern library implementation of alerts, and a bokchoy
test for this functionality.
bmedx/modulestore,bmedx/modulestore,bmedx/modulestore