Issue #2412805 by mondrake: View preview does not attach assets provided by plugins

core/modules/views_ui/src/Tests/PreviewTest.php

core/modules/views_ui/src/ViewPreviewForm.php

core/modules/views_ui/src/ViewUI.php

...ui/tests/modules/views_ui_test/css/views_ui_test.test.css

...i/tests/modules/views_ui_test/views_ui_test.libraries.yml

...views_ui/tests/modules/views_ui_test/views_ui_test.module