ci: fail if there are unconfigured tests
In case we forget to add a test to config (fast, nightly), the test fw prints a warning but the pipeline succeeds. In such a case it should fail instead.
In case it is used for debugging (as mentioned in #249 (closed)), it should be configurable via commandline switch. The debug job would specify this switch. The default should be to fail, i.e. return nonzero.