Add image_id to CRI ContainerStatus message

There is a conversion function `ConvertPodStatusToRunningPod`, which
can override the `Container.ImageID` into a digested reference from the
`ContainerStatus` CRI RPC, which gets mapped from the `image_ref`:

411c29c39f/pkg/kubelet/container/helpers.go (L259-L292)

To avoid that failure case, we now introduce the same `image_id` into
the container status and let runtimes separate the fields.

We also add a note that the mapping from the digested reference of the
CRI to the Kubernetes Pod API `ImageID` field is intentional and should
not change.

Follow-up on: https://github.com/kubernetes/kubernetes/pull/123508

Signed-off-by: Sascha Grunert <sgrunert@redhat.com>

pkg/kubelet/container/runtime.go

@@ -357,6 +357,8 @@ type Status struct {
 	Image string
 	// ID of the image.
 	ImageID string
+	// The digested reference of the image used by the container.
+	ImageRef string
 	// Runtime handler used to pull the image if any.
 	ImageRuntimeHandler string
 	// Hash of the container, used for comparison.