Reorganize Kubernetes clusters action button menu

This commit reorganizes the drop down buttons in the
Agent registration page.

Changelog: changed

app/assets/javascripts/clusters_list/components/clusters_actions.vue

 <script>
-import { GlDropdown, GlDropdownItem, GlModalDirective, GlTooltipDirective } from '@gitlab/ui';
+import {
+  GlDropdown,
+  GlDropdownItem,
+  GlModalDirective,
+  GlTooltipDirective,
+  GlDropdownDivider,
+  GlDropdownSectionHeader,
+} from '@gitlab/ui';
+
 import { INSTALL_AGENT_MODAL_ID, CLUSTERS_ACTIONS } from '../constants';
 
 export default {
@@ -8,6 +16,8 @@ export default {
   components: {
     GlDropdown,
     GlDropdownItem,
+    GlDropdownDivider,
+    GlDropdownSectionHeader,
   },
   directives: {
     GlModalDirective,
@@ -36,15 +46,18 @@ export default {
       split
       right
     >
-      <gl-dropdown-item :href="newClusterPath" data-testid="new-cluster-link" @click.stop>
-        {{ $options.i18n.createNewCluster }}
-      </gl-dropdown-item>
+      <gl-dropdown-section-header>{{ $options.i18n.agent }}</gl-dropdown-section-header>
       <gl-dropdown-item
         v-gl-modal-directive="$options.INSTALL_AGENT_MODAL_ID"
         data-testid="connect-new-agent-link"
       >
         {{ $options.i18n.connectWithAgent }}
       </gl-dropdown-item>
+      <gl-dropdown-divider />
+      <gl-dropdown-section-header>{{ $options.i18n.certificate }}</gl-dropdown-section-header>
+      <gl-dropdown-item :href="newClusterPath" data-testid="new-cluster-link" @click.stop>
+        {{ $options.i18n.createNewCluster }}
+      </gl-dropdown-item>
       <gl-dropdown-item :href="addClusterPath" data-testid="connect-cluster-link" @click.stop>
         {{ $options.i18n.connectExistingCluster }}
       </gl-dropdown-item>

app/assets/javascripts/clusters_list/constants.js

@@ -234,6 +234,8 @@ export const CLUSTERS_ACTIONS = {
   createNewCluster: s__('ClusterAgents|Create a new cluster'),
   connectWithAgent: s__('ClusterAgents|Connect with agent'),
   connectExistingCluster: s__('ClusterAgents|Connect with a certificate'),
+  agent: s__('ClusterAgents|Agent'),
+  certificate: s__('ClusterAgents|Certificate'),
   dropdownDisabledHint: s__(
     'ClusterAgents|Requires a Maintainer or greater role to perform these actions',
   ),