Move pkg/failpoint to internal/failpoint

Signed-off-by: Derek McGowan <derek@mcg.dev>

integration/sandbox_run_rollback_test.go

@@ -35,8 +35,8 @@ import (
 	"github.com/stretchr/testify/require"
 	criapiv1 "k8s.io/cri-api/pkg/apis/runtime/v1"
 
+	"github.com/containerd/containerd/v2/internal/failpoint"
 	"github.com/containerd/containerd/v2/pkg/cri/server/base"
-	"github.com/containerd/containerd/v2/pkg/failpoint"
 )
 
 const (