FRE-600: Fix code review blockers

- Consolidated duplicate UndoManagers to single instance
- Fixed connection promise to only resolve on 'connected' status
- Fixed WebSocketProvider import (WebsocketProvider)
- Added proper doc.destroy() cleanup
- Renamed isPresenceInitialized property to avoid conflict

Co-Authored-By: Paperclip <noreply@paperclip.ing>

node_modules/core-js/modules/esnext.set.of.js

@@ -0,0 +1,10 @@
+'use strict';
+var $ = require('../internals/export');
+var SetHelpers = require('../internals/set-helpers');
+var createCollectionOf = require('../internals/collection-of');
+
+// `Set.of` method
+// https://tc39.github.io/proposal-setmap-offrom/#sec-set.of
+$({ target: 'Set', stat: true, forced: true }, {
+  of: createCollectionOf(SetHelpers.Set, SetHelpers.add, false)
+});