feat: Restore top toolbar compact mode, b=no-bug, c=tabs, compact-mode, common

prefs/compact-mode.yaml

@@ -2,6 +2,12 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
+- name: zen.view.compact.hide-tabbar
+  value: true
+
+- name: zen.view.compact.hide-toolbar
+  value: false
+
 - name: zen.view.compact.toolbar-flash-popup
   value: false