Add CRI API definitions for checkpoint/restore
Add CRI API definitions for checkpoint/restore

This adds the minimal CRI API changes to support checkpoint/restore and
to enable implementation of these checkpoint/restore interfaces on
container engine level.

Signed-off-by: Adrian Reber <areber@redhat.com>

Kubernetes-commit: df4ca2dd9e9fc072f68b1c7b9fd1efdb7a67f593

kubernetes/cri-api