Add tracing spans in CRI image service and pull.go

Signed-off-by: Swagat Bora <sbora@amazon.com>

Add spans around image unpack operations
Use image.ref to denote image name and image.id for the image config digest
Add top-level spand and record errors in the CRI instrumentation service

pkg/cri/server/helpers.go

@@ -92,6 +92,11 @@ const (
 
 	// runtimeRunhcsV1 is the runtime type for runhcs.
 	runtimeRunhcsV1 = "io.containerd.runhcs.v1"
+
+	// name prefix for CRI server specific spans
+	criServerSpanPrefix = "pkg.cri.server"
+
+	spanDelimiter = "."
 )
 
 // makeSandboxName generates sandbox name from sandbox metadata. The name
@@ -510,3 +515,10 @@ func copyResourcesToStatus(spec *runtimespec.Spec, status containerstore.Status)
 	}
 	return status
 }
+
+func makeSpanName(funcName string) string {
+	return strings.Join([]string{
+		criServerSpanPrefix,
+		funcName,
+	}, spanDelimiter)
+}