Clean up and join integration tests

Join the two integration test directories full_test and single_test since there were only two valid test files in single_test anyway. Those two formerly ignored tests are included into the pipeline now. Changes of this MR concern (except for migrating the contents of full_test to integration_tests and adapting the relevant paths accordingly) mainly integration_tests/test_crawler_basics.py (formerly integration_tests/single_test/test_crawler.py.

Tests are executed as explained here