(Backporting this will enable this target to create 1.16-dev)
One of the problems with our current docker tagging is that although we
have strict version tags, latest and dev we do not have a way for docker
users to track the current release branch. This PR simply suggests that
we use the 1.x-dev tag for these and we build and push these. This will
give users who want or need unreleased bug fixes the option of tracking
the pre-release version instead of simply jumping to dev.
(Also contains backport for #18573
zeripath