distrotests: automate packaging tests in GitLab CI

TL;DR

• Schedules can be used to build packages in OBS (knot-resolver-devel, knot-resolver-testing) and execute packaging tests on them
• Environments track which build is deployed in OBS
• When a tag is created, a manual job will appear in its pipeline - click to deploy to knot-resolver-latest; will also run packaging tests afterwards
• In schedules, new variable SKIP_CI variable can be set to 1 to skip execution of regular CI jobs

.gitlab-ci.yml

@@ -508,7 +508,7 @@ obs:build:all:
   script:
     - "osc results home:CZ-NIC:$OBS_REPO knot-resolver -w"
     - >
-      osc results home:CZ-NIC:$OBS_REPO knot-resolver --csv | grep 'succeeded|$' -q || \
+      ! osc results home:CZ-NIC:$OBS_REPO knot-resolver --csv | grep -v 'succeeded' -q || \
         (echo "ERROR: build(s) failed"; exit 1)
 
 .distrotest: &distrotest