Update CoT test data with modern task definitions

[ahal]

The test data being used was generated a long time ago (circa cotv2 and cotv4). To help ensure the tests are relevant we should update the definitions with those from recent tasks.

I'm no expert in this regard, but I think the approach I would take is:

1. Create tests/data/cotv7 (and add associated constants / helper methods to test_cot_verify.py)
2. Save modern task definitions there (e.g, decision task, actions.yml, etc)
3. Attempt to convert as many tests over to this new data as possible
4. Remove cotv2 and cotv4 dirs. It might be fine for some tests to continue using the older data, but having a single data dir would simplify things...
5. Verify no loss in code coverage.