This patch adds support for a container annotation and two separate
pod annotations for controlling the blockio class of containers.
The container annotation can be used by a CRI client:
"io.kubernetes.cri.blockio-class"
Pod annotations specify the blockio class in the K8s pod spec level:
"blockio.resources.beta.kubernetes.io/pod"
(pod-wide default for all containers within)
"blockio.resources.beta.kubernetes.io/container.<container_name>"
(container-specific overrides)
Correspondingly, this patch adds support for --blockio-class and
--blockio-config-file to ctr, too.
This implementation follows the resource class annotation pattern
introduced in RDT and merged in commit 893701220.
Signed-off-by: Antti Kervinen <antti.kervinen@intel.com>