FIX: Rename deprecated icons, allow custom icons in badges

- adds a migration renaming FA4 icon names in badges
- allows all icons to be used in badges (previously was limited to icons prefixed with fa-)
- renames remaining FA 4.7 icons equivalents

app/assets/javascripts/admin/components/admin-web-hook-status.js.es6

@@ -5,7 +5,7 @@ import { bufferedRender } from "discourse-common/lib/buffered-render";
 export default Ember.Component.extend(
   bufferedRender({
     classes: ["text-muted", "text-danger", "text-successful", "text-muted"],
-    icons: ["circle-o", "times-circle", "circle", "circle"],
+    icons: ["far-circle", "times-circle", "circle", "circle"],
 
     @computed("deliveryStatuses", "model.last_delivery_status")
     status(deliveryStatuses, lastDeliveryStatus) {