Create additional NSO_VERSION_MM tags in skeletons

If the current version is marked as tip-of-train (CI variable NSO_VERSION_IS_TOT is set or this is a local build), create additional docker image tags like bgworker/package:MM_$(NSO_VERSION_MM). This allows users of the package to keep using the same include (pinned or not) without having to rebuild the dependency if just the NSO patch version number is changed. For example going from 5.8 to 5.8.3 does not require rebuilding the *.fxs file.

A new CI boolean variable is added to the automatically generated GitLab build jobs: NSO_VERSION_IS_TOT.