hg-git: added base images for tests with Python 3
we'll have one for an unspecified Mercurial version, to be updated to default or stable within the build, and one on Mercurial 5.3
All legacy (hg-git based) Projects have been automatically migrated to native with the upgrade of 2025-01-23
we'll have one for an unspecified Mercurial version, to be updated to default or stable within the build, and one on Mercurial 5.3