versions: Specify forked / vanilla entries of containerd

As we'll need to test with both the vanilla and the forked versions of
containerd, let's make sure we'll specify both entries as part of our
versions.yaml file, and we can read whatever we need accordingly as part
of our tests jobs.

Signed-off-by: Fabiano Fidêncio <fabiano.fidencio@intel.com>

versions.yaml

@@ -221,6 +221,7 @@ externals:
   containerd:
     description: |
       Containerd for Kubernetes Container Runtime Interface.
+    forked:
       # CCv0 is using our fork of containerd as the changes can't be merged yet
       # DO NOT TOUCH DURING MERGES FROM MAIN TO CCv0
       url: "github.com/confidential-containers/containerd"
@@ -229,6 +230,14 @@ externals:
       version: "v1.6.8.2"
       # CCv0 needs to know about the specific branch for the integration tests
       branch: "CC-main"
+    upstream:
+      # DO NOT TOUCH DURING MERGES FROM MAIN TO CCv0
+      url: "github.com/containerd/containerd"
+      # yamllint disable-line rule:line-length
+      tarball_url: "https://github.com/containerd/containerd/releases/download"
+      version: "v1.6.8"
+      # CCv0 needs to know about the specific branch for the integration tests
+      branch: "release/1.6"
 
   critools:
     description: "CLI tool for Container Runtime Interface (CRI)"