Add Arch-based Docker test setup, shallow clone mode support and pkgmgr tests (see ChatGPT conversation: https://chatgpt.com/share/693052a1-edd0-800f-a9d6-c154b8e7d8e0)

.github/workflows/test.yml

@@ -0,0 +1,25 @@
+name: Test package-manager
+
+on:
+  push:
+    branches:
+      - main
+      - master
+      - develop
+      - "*"
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Show Docker version
+        run: docker version
+
+      - name: Run tests via make (builds Docker image and runs unit + integration tests)
+        run: make test