Issue #1946208 by dawehner: Rewrite QueryGroupByTest to use ViewUnitTestBase.

...es/system/tests/modules/entity_test/entity_test.views.inc

...modules/views/lib/Drupal/views/Tests/QueryGroupByTest.php

...modules/views/lib/Drupal/views/Tests/ViewUnitTestBase.php

...est_config/test_views/views.view.test_aggregate_count.yml

...test_config/test_views/views.view.test_group_by_count.yml

...config/test_views/views.view.test_group_by_in_filters.yml