ESR115: figure out extension pinning / unified Extensions

IIUIC we don't ship with NoScript on the toolbar (and in the past we also removed HTTPS-Everywhere?) - not sure of the full reasons, but width is at a premium and I believe the idea was to get users to use the slider, not NS itself. Correct me if I'm wrong

user_pref("extensions.unifiedExtensions.enabled", false);

Note: there's 1808459 Unified Extensions when empty ignores extensions.getAddons.showPane - but hopefully that will be fixed come ESR115