Refactor kustomize config command structure

- Create cfg, fn, live parent commands

cmd/config/configcobra/fn.go

@@ -0,0 +1,24 @@
+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package configcobra
+
+import (
+	"github.com/spf13/cobra"
+	"sigs.k8s.io/kustomize/cmd/config/internal/commands"
+)
+
+func GetFn(name string) *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "fn",
+		Short: "Commands for running functions against configuration.",
+	}
+
+	cmd.AddCommand(commands.RunCommand(name))
+	cmd.AddCommand(commands.SinkCommand(name))
+	cmd.AddCommand(commands.SourceCommand(name))
+	cmd.AddCommand(commands.WrapCommand())
+	cmd.AddCommand(commands.XArgsCommand())
+
+	return cmd
+}