Runsc shim grouping per pod.

Enable grouping in runsc shim, changes include:
- Checking the kubernetes level annotation to identify if grouping should be
supported.
- All the TaskService methods implemented by the runsc service are modified to
store the containers within the sandbox, retrieve the container process when
necessary to perform the related actions.

PiperOrigin-RevId: 796987334

Author: nybidari