feat: get nodeList from k8s

nextflow/plugins/nf-k8s/src/main/nextflow/k8s/client/K8sClient.groovy

@@ -523,6 +523,17 @@ class K8sClient {
         throw new K8sResponseException("K8s undetermined status conditions for pod $podName", resp)
     }
 
+    /**
+     * Get list of all nodes in the cluster
+     * @return Response object.
+     */
+    K8sResponseJson nodeList() {
+        final action = "/api/v1/nodes"
+        final resp = get(action)
+        trace('GET', action, resp.text)
+        new K8sResponseJson(resp.text)
+    }
+
     protected void checkInvalidWaitingState( Map waiting, K8sResponseJson resp ) {
         if( waiting.reason == 'ErrImagePull' || waiting.reason == 'ImagePullBackOff') {
             def message = "K8s pod image cannot be pulled"