MDL-47494 ddwtos: Improve the drag-drop question Behat tests.
* Added tests for previewing the question, to make sure it works when attempted. * Added Moodle XML export tests. * Reorganised the tests to follow the 'Test one thing per scenario' best practice. This commit requires MDL-49154 to work.
question/type/ddwtos/tests/behat/import_test.feature → question/type/ddwtos/tests/behat/import.feature