Single CI/CD pipeline definitions

With this MR, we replace our per-subproject CI/CD pipeline definitions by a central pipeline for all subprojects. The main reason for this is that triggering child pipelines does not work as intended. We always had issues with failing pipelines if changes in merge requests were not successfully captures and also the visualization for parent/child pipelines is bad. It is likely that at some point we might switch back to individual pipelines per subproject, but for now this solutions seems to be best in relation to effort.

This MR also does:

• Closes #51 (closed)
• Closes #124 (closed)

changed milestone to %0.4.0

added modul/infrastructure label

changed the description

added 31 commits

• bf765ee1...d6f1ee42 - 30 commits from branch master
• 526f520c - Merge remote-tracking branch 'origin/master' into single-ci-pipeline

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added 1 commit

• 50b9e76f - Add build job dependency for subsequent jobs

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mentioned in commit d65f3e8e

merged

mentioned in commit 0735d740