[EE] Add users search results to global search

What does this MR do?

EE version of https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/21197

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• EE specific content should be in the top level /ee folder
• For a paid feature, have we considered GitLab.com plans, how it works for groups, and is there a design for promoting it to users who aren't on the correct plan?
• Security reports checked/validated by reviewer

app/views/search/_category.html.haml

+- users = capture_haml do
+  - if can?(current_user, :read_users_list)
+    %li{ class: active_when(@scope == 'users') }
+      = link_to search_filter_path(scope: 'users') do
+        Users
+        %span.badge.badge-pill
+          = limited_count(@search_results.limited_users_count)
+
 .scrolling-tabs-container.inner-page-scroll-tabs.is-smaller
   .fade-left= icon('angle-left')
   .fade-right= icon('angle-right')
@@ -45,12 +53,7 @@
             = _("Commits")
             %span.badge.badge-pill
               = @search_results.commits_count
-      - if can?(current_user, :read_users_list)
-        %li{ class: active_when(@scope == 'users') }
-          = link_to search_filter_path(scope: 'users') do
-            Users
-            %span.badge.badge-pill
-              = limited_count(@search_results.limited_users_count)
+      = users
 
     - elsif @show_snippets
       %li{ class: active_when(@scope == 'snippet_blobs') }
@@ -84,9 +87,4 @@
           = _("Milestones")
           %span.badge.badge-pill
             = limited_count(@search_results.limited_milestones_count)
-      - if can?(current_user, :read_users_list)
-        %li{ class: active_when(@scope == 'users') }
-          = link_to search_filter_path(scope: 'users') do
-            Users
-            %span.badge.badge-pill
-              = limited_count(@search_results.limited_users_count)
+      = users