Iss1521 - Allow users to bulk test a quiz

[EJMFarrow]

• Allow users with question:editall permission on a quiz context to run a bulk test on all the questions of a quiz.
• There's a new link from STACK dashboard to a page listing all the quizzes containing a question. Clicking a specific quiz runs the test for that quiz.
• Will test all the questions in random selections.
• It looks like there are lots of changes to bulktester class but it's mainly separating out the testing of an individual question into its own function. Comparing in VS Code gives a better impression of what's going on.

#1521

[sangwinc]

Thanks @EJMFarrow that's really very helpful. This makes it so much easier to test the relevant questions. Much appreciated.