test: provide node discovery for cli tests via kubectl

Fixes #2330

CLI tests require node discovery as `--nodes` flag is enforced for most
of the `talosctl commands`.

For clusters created via `talosctl cluster create`, cluster provisioner
state provides all the necessary information, but clusters created via
CAPI don't have the state attached.

API tests rely on Talos and Kubernetes APIs to fetch kubeconfig and
access Nodes K8s API.

CLI tests should rely only on CLI tools, so we use `kubectl get nodes` +
`talosctl kubeconfig` to fetch list of master and worker nodes.

This discovery method relies on "bootstrap" node being set in
`talosconfig` (to fetch `kubeconfig`).

Signed-off-by: Andrey Smirnov <smirnov.andrey@gmail.com>

internal/integration/base/cluster.go

@@ -0,0 +1,31 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+// +build integration
+
+package base
+
+import "github.com/talos-systems/talos/internal/app/machined/pkg/runtime"
+
+type infoWrapper struct {
+	masterNodes []string
+	workerNodes []string
+}
+
+func (wrapper *infoWrapper) Nodes() []string {
+	return append(wrapper.masterNodes, wrapper.workerNodes...)
+}
+
+func (wrapper *infoWrapper) NodesByType(t runtime.MachineType) []string {
+	switch t {
+	case runtime.MachineTypeInit:
+		return nil
+	case runtime.MachineTypeControlPlane:
+		return wrapper.masterNodes
+	case runtime.MachineTypeJoin:
+		return wrapper.workerNodes
+	default:
+		panic("unreachable")
+	}
+}