Add a test ensuring that TypeReps can be stored in compact regions
My work thus far on D4085 has involved
TypeReps with cyclical structure. That bit me in
:force doesn't work with cyclical structures. This would also have caused trouble for storing
TypeReps in compact regions. If we eventually make
:force work with cyclical structures (see #14400), then cyclical
TypeReps won't break the test suite but might break user code using compact regions. So let's test for that.