Extract ee-only code under /ee dir

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/controllers/admin/dashboard_controller.rb

 class Admin::DashboardController < Admin::ApplicationController
+  prepend ::EE::Admin::DashboardController
+
   def index
     @projects = Project.order_id_desc.without_deleted.with_route.limit(10)
     @users = User.order_id_desc.limit(10)
     @groups = Group.order_id_desc.with_route.limit(10)
     @license = License.current
-
-    # EE only
-    @admin_count = User.admins.count
-    @roles_count = ProjectAuthorization.roles_stats
   end
 end

ee/app/controllers/ee/admin/dashboard_controller.rb

+# rubocop:disable Gitlab/ModuleWithInstanceVariables
+module EE
+  module Admin
+    module DashboardController
+      extend ActiveSupport::Concern
+
+      prepended do
+        before_action :set_roles_count, only: [:index]
+      end
+
+      private
+
+      def set_roles_count
+        @admin_count = ::User.admins.count
+        @roles_count = ::ProjectAuthorization.roles_stats
+      end
+    end
+  end
+end

ee/app/views/admin/dashboard/_roles_stats.html.haml

-%div
+- if @admin_count
   %p
     Admin users
     %span.light.pull-right
       = @admin_count
 
+- if @roles_count
   - @roles_count.reverse_each do |row|
     %p
       Users with highest role
-      %strong #{row['kind']}
+      %strong
+        = row['kind']
       %span.light.pull-right
         = row['amount']