Add descriptor tests for @counter-style

[Zefling]

I had to make lots of exceptions to be able to test @counter-style completely. I don't know if it can be accepted.

[LeaVerou]

thank you for working on this. However, I don't think adding exceptions for specific rules in the testing code is a good way forward. Instead of making exceptions for specific rules, we should add extensibility points so that the tests that need exceptions can define whatever exceptions they need themselves. Otherwise, if in the future we need to make more exceptions, the code will become a mess.

[Zefling]

I changed for rules in tests.js

[Zefling]

@LeaVerou Is it not good ?