The release workflows did not run checkout with `fetch-tags: true`, so
the builds were unable to compute the correct release version number. I
audited all instances of `actions/checkout` to add `fetch-tags` where
needed and clean up unneeded options.
I also had to fix options to `docker/build-push-action`, which by
default ignores `actions/checkout` and tries to pull from git itself.
This led to the Docker build running in a context without the new tag.
Finally, to make verification easier and provide version info in the
build logs, this adds debugging info to the version-generation script
via stderr.
Closes#1366
d83c7b1d45