Class test common data urls

[joseph-palmer]

Removes common_data_urls from the expected country fields of test-check_country_class and adds a new test that either common_data_urls or level_data_urls is defined in each class. Also removed common_data_urls from classes where it was empty and only there to pass the previous tests.

closes #339

[github-actions[bot]]

👋 Thanks for opening this pull request! Can you please run through the following checklist before requesting review (ticking as complete or if not relevant).

• [x] Read our contribution guidelines if you have not already done so.
  • [ ] If you have altered an existing class please run the tests locally (using devtools::load_all(); devtools::test()) first setting options(testDownload=TRUE, testSource=class-name) and report your findings.
  • [x] If you have added a new data class please run the tests locally for that class (using devtools::load_all(); devtools::test()).
  • [ ] Check your code passes our CI checks and review any style and code coverage warnings.
  • [ ] Comment with details if unable to get our CI checks to pass or unable to remove all warnings.

Thank you again for the contribution. If making large scale changes consider using our pre-commit hooks (see the contributing guide) to more easily comply with our guidelines.