issue #20476: fixed tax assignment list

This bug was due to the problem of the dots in the attr field not lining up right with the isNested-ness of the ORM. We've seen this before, so I added a test that will look at every list and make sure that none of them are miswired. I ended fixing about 4 other lists too, which failed the test. I also had to add a model->cache registry, like our model->list and model->workspace registries.