Produce intermediate devel builds for all production flavors
This MR originally aims at adding a devel build of ge21_ctp7
in order to be able to install the last firmware version at p5 for the GE2/1 demonstrator. Some more clean-up and uniformization of the devel builds GitLab CI file has been introduced.
Also includes the original !69 (closed) that is required to run with ZS enable at p5.