Migrate from urfave/cli to cobra (#426)

* wip

* env var fix

* cluster create

* cluster create and delete

* cluster list

* cluster cmd

* kubeconfig

* policy create

* policy delete and list, and added root commands

* removed urfavecli from k3kcli

* fix policy command

* k3k-kubelet to cobra

* updated docs

* updated go.mod

* updated test

* added deletion

* added cleanup and flake attempts

* wip bind env

* simplified config

cli/main.go

@@ -1,16 +1,14 @@
 package main
 
 import (
-	"os"
-
 	"github.com/sirupsen/logrus"
 
 	"github.com/rancher/k3k/cli/cmds"
 )
 
 func main() {
-	app := cmds.NewApp()
-	if err := app.Run(os.Args); err != nil {
+	app := cmds.NewRootCmd()
+	if err := app.Execute(); err != nil {
 		logrus.Fatal(err)
 	}
 }