ci: Add a default retry policy for jobs

Automatically retry if it's a system failure or similar

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/1736>

.gitlab-ci.yml

@@ -38,6 +38,14 @@ workflow:
 
 default:
   interruptible: true
+  # Auto-retry jobs in case of infra failures
+  retry:
+    max: 1
+    when:
+      - 'runner_system_failure'
+      - 'stuck_or_timeout_failure'
+      - 'scheduler_failure'
+      - 'api_failure'
 
 stages:
   - "trigger"