chore: Cover displaying Product Attributes by tests

Problem/Motivation

We implemented the displaying product attributes feature, but not covered it by test.

So we need to cover it by the current separate task.

Cover these pages:

- product page
- order page
- cart page
- product catalog (facets)

Try to write the single universal checking function and reuse it in tests, extending the current smoke tests.

To get the list of chosen attributes, we can create a separate endpoint in the commercetools_test module, that will give us a json with the current settings, using thDrupalFetchURL function.