Better test coverage of course/user report sources

The current course/user reports sources are only being tested via the course/user entities respectively (the courses test is also testing base entity implementation)

There need to be tests of each entire report source, column/filters/etc from each entity added to them (example)

Found while working on MDL-75245 (I've started some of the report source tests there, should be finished here)

Note this blocks MDL-75359, see this comment