feat(kubeconfig): kubeconfig download functionality EE-1202 (#5386)

* backend migration/backport

* Feat(kubeconfig): kubeconfig download button frontend EE-1202 (#5385)

* kubeconfig download button frontend

* fix kubeconfig download button

* backend migration/backport

* moved ng-if up one level

Co-authored-by: zees-dev <dev.786zshan@gmail.com>

* resolved conflicts, updated code

* - kube-config -> kube-config-download-button
- fixed kubeconfig file name (bug)

Co-authored-by: Richard Wei <54336863+WaysonWei@users.noreply.github.com>

app/kubernetes/components/kubectl-shell/kubectl-shell.html

@@ -1,14 +1,12 @@
 <button type="button" class="btn btn-xs btn-primary" ng-click="$ctrl.connectConsole()" ng-disabled="$ctrl.state.shell.connected" data-cy="k8sSidebar-shellButton">
-  <i class="fa fa-terminal" style="margin-right: 2px;"></i>
-  kubectl shell
+  <i class="fa fa-terminal space-right"></i> kubectl shell
 </button>
 
+<kube-config-download-button></kube-config-download-button>
+
 <div ng-if="$ctrl.state.checked" class="{{ $ctrl.state.css }}-kubectl-shell">
   <div class="shell-container">
     <div class="shell-item"><i class="fas fa-terminal" style="margin-right: 5px;"></i>kubectl shell</div>
-    <div ng-if="$ctrl.state.isHTTPS" class="shell-item-center">
-      <a href="" ng-click="$ctrl.downloadKubeconfig()"><i class="fas fa-file-download" style="margin-right: 5px;"></i>Download Kubeconfig</a>
-    </div>
     <div class="shell-item-right">
       <i class="fas fa-redo-alt" ng-click="$ctrl.screenClear();" data-cy="k8sShell-refreshButton"></i>
       <i