RHOAIENG-15772: tests(odh-nbc): write envtest kubeconfig to disk upon…

… request

This helps with debugging because it's then possible to do e.g.

```
KUBECONFIG=/tmp/envtest.kubeconfig k9s
```

and investigate the cluster while the test is paused on a breakpoint.

components/odh-notebook-controller/controllers/suite_test.go

@@ -19,6 +19,7 @@ import (
 	"crypto/tls"
 	"fmt"
 	"net"
+	"os"
 	"path/filepath"
 	"testing"
 	"time"
@@ -129,6 +130,16 @@ var _ = BeforeSuite(func() {
 	})
 	Expect(err).NotTo(HaveOccurred())
 
+	if kubeconfigPath, found := os.LookupEnv("DEBUG_WRITE_KUBECONFIG"); found {
+		user := envtest.User{Name: "MasterOfTheSystems", Groups: []string{"system:masters"}}
+		authedUser, err := envTest.ControlPlane.AddUser(user, nil)
+		Expect(err).NotTo(HaveOccurred())
+		config, err := authedUser.KubeConfig()
+		Expect(err).NotTo(HaveOccurred())
+		err = os.WriteFile(kubeconfigPath, config, 0600)
+		Expect(err).NotTo(HaveOccurred())
+	}
+
 	// Setup notebook controller
 	err = (&OpenshiftNotebookReconciler{
 		Client: mgr.GetClient(),