Create ci/cd for retention as addon

we are working to have the retention work as a dedicated add on with both a master branch and a maintenance branch. Work is being done to decouple the retention work for 11.x into a separate repository.

per email from Thomas, we will only move "master" to a new repo at this time (10.10 will remain as part of the platform/HF release cycle). As we are getting closer to release of the new platform, it would make sense to establish two ci/cd chains eventually, one for maintenance and one for master.