fix: add warning about not run tests due to failed fixtures

See problem in lhcb/LHCb!3321 (merged)

The issue is that I wasn't properly differentiating the various causes of a Status=notrun.
All notrun tests were being ignored, assuming I can't do anything for them anyway. Which is true for e.g. those that are disabled/skipped.

But the problematic category are those tests which get notrun because one of their test dependencies failed. In that case, the test which wasn't run might actually also be in need of a reference update.
This MR isn't a true fix yet, as I'm not sure how to best handle it yet. It might require some changes of the test reporting in LHCb and can't just be fixed with changes here.

But this MR does add a warning for tests which aren't run due to a failed dependency, thus at least making us aware that the ref updates might not be complete.