Lift most test cases to the new syntax, just with few exceptions:
- tests/test_refspec/test2.yml actually stresses the mixed usage
(but clean per repo)
- tests/test_repo_includes references kas as external repo at a point
where there was no new syntax yet; this needs to be migrated
differently later on
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>