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

added 1 commit

• d2bad695 - gitlabci: fix incorrect result of obs:build:all

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added 2 commits

• 2455a51b - gitlabci: fail obs:build:all on mismatching versions
• dba8c226 - gitlabci: make version mismatch more obvious in obs:* jobs

Compare with previous version

added 20 commits

• dba8c226...d093bb23 - 4 commits from branch master
• 1cd179a0 - distro/tests: limit CPU and memory for VMs
• f47cded9 - distro/tests: add fedora30, ubuntu1904
• d324b2db - distro/tests: remove pkgtests for rolling distros
• 11dbb13e - distro/tests: support test-distro.sh exec from any directory
• 00d72ef7 - scripts/obs-build.sh: support build for different repos
• 8d143acd - distro/tests: support more OBS repos in test-distro.sh
• a0b48cce - gitlabci: add SKIP_CI variable
• 31ef622f - scripts/make-distrofiles.sh: remove obsolete -s switch
• d8e3bbbe - gitlabci: add distrotests to CI
• beaed323 - gitlabci: add OBS build check (all archs+distros)
• 54d5f1cd - gitlabci: support OBS build in knot-resolver-latest on tags
• 80b21ff2 - gitlabci: reorganize & cleanup
• 1c234135 - distro/tests: remove fedora28, ubuntu1810 (eol)
• dd1d15b3 - gitlabci: fix incorrect result of obs:build:all
• 4eefc556 - gitlabci: fail obs:build:all on mismatching versions
• e8428fae - gitlabci: make version mismatch more obvious in obs:* jobs

Compare with previous version

resolved all discussions

merged

mentioned in commit 750c76ee

I passed through it all quickly, and it looks good. I trust it doesn't really need more in-depth review.