Move the release-helper from the CNG repo here
It's easier to be able to make changes to the script at dsop release time, rather than needing to make the change in CNG and get a new patch release. This is part of why the script is moving here.
I used this change for the recent release of 13.5.0 to dsop.
This is basically a copy of https://gitlab.com/gitlab-org/build/CNG/-/blob/master/build-scripts/ubi-offline/release-helper.sh with the initial variables preset to the new locations.