Update views for testability

Also, prettify one of them.

app/assets/javascripts/vue_shared/components/sidebar/labels_select/base.vue

@@ -167,7 +167,7 @@ dropdown-menu-labels dropdown-menu-selectable"
           <div class="dropdown-page-one">
             <dropdown-header v-if="showCreate" />
             <dropdown-search-input />
-            <div class="dropdown-content"></div>
+            <div class="dropdown-content" data-qa-selector="labels_dropdown_content"></div>
             <div class="dropdown-loading"><gl-loading-icon /></div>
             <dropdown-footer
               v-if="showCreate"

app/assets/javascripts/vue_shared/components/sidebar/labels_select/dropdown_title.vue

@@ -14,7 +14,11 @@ export default {
     {{ __('Labels') }}
     <template v-if="canEdit">
       <i aria-hidden="true" class="fa fa-spinner fa-spin block-loading" data-hidden="true"> </i>
-      <button type="button" class="edit-link btn btn-blank float-right js-sidebar-dropdown-toggle">
+      <button
+        type="button"
+        class="edit-link btn btn-blank float-right js-sidebar-dropdown-toggle"
+        data-qa-selector="labels_edit_button"
+      >
         {{ __('Edit') }}
       </button>
     </template>