Wire through CRI ContainerCheckpoint RPC

This connects the new CRI ContainerCheckpoint RPC to the existing
internal checkpoint functions. With this commit it is possible
to checkpoint a container in Kubernetes using the Forensic Container
Checkpointing KEP (#2008):

 # curl X POST "https://localhost:10250/checkpoint/namespace/podId/container"

Which will result in containerd creating a checkpoint in the location
specified by Kubernetes (usually /var/lib/kubelet/checkpoints).

This is a Linux only feature because CRIU only exists on Linux.

Rewritten with the help of Phil Estes.

Signed-off-by: Phil Estes <estesp@gmail.com>
Signed-off-by: Adrian Reber <areber@redhat.com>

vendor/github.com/checkpoint-restore/go-criu/v7/features.go

@@ -0,0 +1,45 @@
+package criu
+
+import (
+	"fmt"
+
+	"github.com/checkpoint-restore/go-criu/v7/rpc"
+)
+
+// Feature checking in go-criu is based on the libcriu feature checking function.
+
+// Feature checking allows the user to check if CRIU supports
+// certain features. There are CRIU features which do not depend
+// on the version of CRIU but on kernel features or architecture.
+//
+// One example is memory tracking. Memory tracking can be disabled
+// in the kernel or there are architectures which do not support
+// it (aarch64 for example). By using the feature check a libcriu
+// user can easily query CRIU if a certain feature is available.
+//
+// The features which should be checked can be marked in the
+// structure 'struct criu_feature_check'. Each structure member
+// that is set to true will result in CRIU checking for the
+// availability of that feature in the current combination of
+// CRIU/kernel/architecture.
+//
+// Available features will be set to true when the function
+// returns successfully. Missing features will be set to false.
+
+func (c *Criu) FeatureCheck(features *rpc.CriuFeatures) (*rpc.CriuFeatures, error) {
+	resp, err := c.doSwrkWithResp(
+		rpc.CriuReqType_FEATURE_CHECK,
+		nil,
+		nil,
+		features,
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	if resp.GetType() != rpc.CriuReqType_FEATURE_CHECK {
+		return nil, fmt.Errorf("unexpected CRIU RPC response")
+	}
+
+	return features, nil
+}