ci: publish multi-arch image manifest lists (#4254)

This change adds linux/arm64 binaries to the release. It also publishes an arm64
container image for all variants (standard, debug, rootless, static) and releases
(dev, edge, latest).

The build and push process uses buildx in order to push the individual
images by digest (i.e. untagged) and reference them in a single, tagged manifest
list. This avoids cluttering Docker Hub's tag list with `<tag>-<arch>` tags.

Fixes #2233

Signed-off-by: Nick Graef <1031317+ngraef@users.noreply.github.com>