Accept more content types of Docker manifests (#2758)

The old code accepts only
application/vnd.docker.distribution.manifest.v2+json and
application/vnd.oci.image.manifest.v1+json, but GCP artifact registry
returns application/vnd.oci.image.index.v1+json for
gcr.io/bazel-public/ubuntu2404

Should fix issues such as
https://buildkite.com/bazel/bazel-bazel-github-presubmit/builds/35379#019fcd81-ba85-4e4a-a516-6b889a3851bd