UI ember engines (#6718)

Adds replication engine and core in-repo addon

ui/lib/replication/addon/controllers/replication-mode.js

@@ -0,0 +1,16 @@
+import { alias } from '@ember/object/computed';
+import { inject as service } from '@ember/service';
+import Controller from '@ember/controller';
+
+export default Controller.extend({
+  rm: service('replication-mode'),
+  replicationMode: alias('rm.mode'),
+  actions: {
+    onEnable(mode) {
+      return this.transitionToRoute('mode', mode);
+    },
+    onDisable() {
+      return this.transitionToRoute('index');
+    },
+  },
+});