Reapply "Switch container factory to webpack"

This reverts commit 18d93b00ba.

cms/templates/edit-tabs.html

@@ -19,10 +19,10 @@
 % endfor
 </%block>
 
-<%block name="requirejs">
-    require(["js/factories/edit_tabs"], function (EditTabsFactory) {
+<%block name="page_bundle">
+    <%static:webpack entry="js/factories/edit_tabs">
         EditTabsFactory("${context_course.location | n, js_escaped_string}", "${reverse('tabs_handler', kwargs={'course_key_string': context_course.id})}");
-    });
+    </%static:webpack>
 </%block>
 
 <%block name="content">