[TESTS:] Change test fixtures to run tests on all supported languages dynamically.

[ByteOtter]

You would like to suggest a new feature?

Currently our test data is provided by pytest.fixtures which only return static sample values. However, we want to test all of nester's functions on all supported languages so we have to change the fixture to return the list of lanugages provided by utils.detect_languages() and change the tests to run again and again until all languages are done.