[ci] use matrix for different setups

5 jobs for !2835 with feature/simplify-ci
latest detached
Status Name Job ID Coverage
  Trigger
passed test-trigger: [$IMAGE_REGISTRY_URL/full:dune-2.7-clang-ubuntu-20.04]

passed test-trigger: [$IMAGE_REGISTRY_URL/full:dune-2.7-gcc-ubuntu-20.04]

passed test-trigger: [$IMAGE_REGISTRY_URL/full:dune-master-gcc-ubuntu-20.04]

passed test-trigger: [$IMAGE_REGISTRY_URL/minimal:dune-2.7-gcc-ubuntu-20.04]

 
  Downstream Modules
passed trigger lecture