Support downloading OCI Artifact manifest

[northtyphoon]

Need to update ORAS-GO module to v2.0.0-rc.5 and above to support OCI Artifact manifest.

Scenarios:

• Download ORAS v0.16.0 from https://github.com/oras-project/oras/releases/tag/v0.16.0

• Use ORAS to push an OCI Artifact to ACR

  echo "FROM mcr.microsoft.com/hello-world" > hello-world.dockerfile
  oras push myregistry.azurecr.io/dockerfile:1.0 hello-world.dockerfile

• Run acb to download the OCI Artifact

  acb download oci://myregistry.azurecr.io/dockerfile:1.0 ...

Expected: Download the artifact successfully.