pkg/cri: split out NRI API from pkg/cri/server.

Split out the criService-agnostic bits of nri-api* from
pkg/cri/server to pkg/cri/nri to allow sharing a single
implementation betwen the server and sbserver versions.
Rework the interfaces to not require access to package
internals.

Signed-off-by: Krisztian Litkey <krisztian.litkey@intel.com>

pkg/cri/server/sandbox_stop.go

@@ -82,11 +82,9 @@ func (c *criService) stopPodSandbox(ctx context.Context, sandbox sandboxstore.Sa
 	}
 	sandboxRuntimeStopTimer.WithValues(sandbox.RuntimeHandler).UpdateSince(stop)
 
-	if c.nri.isEnabled() {
-		err := c.nri.stopPodSandbox(ctx, &sandbox)
-		if err != nil {
-			log.G(ctx).WithError(err).Errorf("NRI sandbox stop notification failed")
-		}
+	err := c.nri.StopPodSandbox(ctx, &sandbox)
+	if err != nil {
+		log.G(ctx).WithError(err).Errorf("NRI sandbox stop notification failed")
 	}
 
 	// Teardown network for sandbox.