Suggest renaming tests top to t and adding --bad or otherwise

[wsnyder]

• Can you consider renaming "module top" in your tests to "module t"? This makes us able to run your tests under the Verilator test framework without changes. (We can work around this by making something like your guess_top_module if there's a reason you prefer "top", but prefer not to, as "TOP" means something different already in the verilator tests.)

• Verilator tests have _bad in the tests that are expected to fail, I note some of yours have _inv, but not all. It would make it easier to triage these if you consitently named with something (-fail, or whatever). Another step nicer would be to have ":should_fail:" default if not specified to just look for the _inv in the filename.