[7.8 backport] Cannot deploy artifacts with sources without help

Backport of CMS7-9128
This requires an update of the 7.8 project-pom and therefore a bump of the parent pom for all projects...

Temporary workaround is using $mvn release:perform -DuseReleaseProfile=false but this has as consequence/side-effect that -javadoc.jar artifacts no longer get build and deployed... (except if this is configured specifically for the project itself)