[CI] deduplicate renderer tests
Short renderer tests were introduced by duplicating the tests/renderer directory to tests/renderer_short. For easier maintenance, instead only duplicate the test_renderer[_short].py file.
WARNING! Gitlab maintenance operation scheduled for Monday, 20 April between 12:00 and 14:00 (CET). During this time window, short service interruptions (less than 5 minutes) may occur. Thank you in advance for your understanding.
Short renderer tests were introduced by duplicating the tests/renderer directory to tests/renderer_short. For easier maintenance, instead only duplicate the test_renderer[_short].py file.