ci: use osbuild/containers images

Use the images provided by `osbuild/containers` tagged as GHCI (GitHub
CI). These images are fully under our control, cached on the GitHub
infrastructure, and prepared to run `systemd-nspawn` and friends in a
docker container.

The GHCI infrastructure is versioned. New updates to the CI
infrastructure are not automatically picked up. Instead, the `v1` tag
has to be explicitly redirected to new image builds to deploy them. If
a new deployment causes CI failures, we can simply redirect the `v1` tag
back to the previous image builds and get the previous behavior back.

The `osbuild/containers` repository contains the required
infrastructure for this logic. If new dependencies are required in the
CI environment, the respective Dockerfiles must be updated. As a
temporary workaround (e.g., as part of a PR that introduces this), you
can simply add `dnf install -y <package>` to the required entries in
`.github/workflows/*`.

.github/workflows/runtime-tests.yml

@@ -17,24 +17,10 @@ jobs:
     steps:
     - name: "Clone Repository"
       uses: actions/checkout@v2
-    - name: "Install Dependencies"
-      run: |
-        sudo apt-get update
-        sudo apt-get -y install \
-          nbd-client \
-          qemu-utils \
-          rpm \
-          systemd-container \
-          tar \
-          yum
-    - name: "Set up Python"
-      uses: actions/setup-python@v1
-      with:
-        python-version: 3.7
-    - name: Install Python Packages
-      run: pip install jsonschema
     - name: "Run Pipeline Tests"
-      run: sudo env "PATH=$PATH" make test-runtime
+      uses: osbuild/containers/ghci/actions/ghci-osbuild@ghci/v1
+      with:
+        run: make test-runtime
 
   noop_pipeline_tests:
     name: "Noop-Pipeline Tests"