[Attributor] Properly repair broken unittest

Reverts 2dc7c709 and instead repairs the
unittest properly. The test was broken as that it used references to
dead functions, assumed dead functions could reach code, assumed code
would not be deleted, and did not pre-query all assertion queries.
Arguably, the querry AAs don't make it easy to use them outside the
attributor pipeline, maybe we just should not (or should fix them
pessimistically). For now, the unittest is fixed.