Revert "remove-DOMContentLoaded-clusters-Pages"

This reverts merge request !47799

app/assets/javascripts/pages/groups/clusters/destroy/index.js

 import ClustersBundle from '~/clusters/clusters_bundle';
 
-new ClustersBundle(); // eslint-disable-line no-new
+document.addEventListener('DOMContentLoaded', () => {
+  new ClustersBundle(); // eslint-disable-line no-new
+});

app/assets/javascripts/pages/groups/clusters/edit/index.js

 import ClustersBundle from '~/clusters/clusters_bundle';
 
-new ClustersBundle(); // eslint-disable-line no-new
+document.addEventListener('DOMContentLoaded', () => {
+  new ClustersBundle(); // eslint-disable-line no-new
+});

app/assets/javascripts/pages/groups/clusters/index.js

 import initCreateCluster from '~/create_cluster/init_create_cluster';
 import initIntegrationForm from '~/clusters/forms/show/index';
 
-initCreateCluster(document, gon);
-initIntegrationForm();
+document.addEventListener('DOMContentLoaded', () => {
+  initCreateCluster(document, gon);
+  initIntegrationForm();
+});

app/assets/javascripts/pages/groups/clusters/index/index.js

 import PersistentUserCallout from '~/persistent_user_callout';
 import initClustersListApp from '~/clusters_list';
 
-const callout = document.querySelector('.gcp-signup-offer');
-PersistentUserCallout.factory(callout);
-initClustersListApp();
+document.addEventListener('DOMContentLoaded', () => {
+  const callout = document.querySelector('.gcp-signup-offer');
+  PersistentUserCallout.factory(callout);
+  initClustersListApp();
+});

app/assets/javascripts/pages/groups/clusters/new/index.js

 import initNewCluster from '~/clusters/new_cluster';
 
-initNewCluster();
+document.addEventListener('DOMContentLoaded', () => {
+  initNewCluster();
+});

app/assets/javascripts/pages/groups/clusters/show/index.js

 import ClustersBundle from '~/clusters/clusters_bundle';
 import initClusterHealth from '~/pages/projects/clusters/show/cluster_health';
 
-new ClustersBundle(); // eslint-disable-line no-new
-initClusterHealth();
+document.addEventListener('DOMContentLoaded', () => {
+  new ClustersBundle(); // eslint-disable-line no-new
+  initClusterHealth();
+});