test: make the test case failure output easier to select

Split the suite and test case name up so it's easier to select with a
double-click in the terminal. Because usually those tests need to be re-run
individually and making that easier is a good thing.

Previously:
:: Failure: ../test/test-tablet.c:4434:touch_arbitration:wacom-cintiq-13hdt-pen-tablet

Now:
:: Failure: ../test/test-tablet.c:4434: touch_arbitration(wacom-cintiq-13hdt-pen-tablet)

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>