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/es.set.is-subset-of.v2.js

@@ -0,0 +1,14 @@
+'use strict';
+var $ = require('../internals/export');
+var isSubsetOf = require('../internals/set-is-subset-of');
+var setMethodAcceptSetLike = require('../internals/set-method-accept-set-like');
+
+var INCORRECT = !setMethodAcceptSetLike('isSubsetOf', function (result) {
+  return result;
+});
+
+// `Set.prototype.isSubsetOf` method
+// https://tc39.es/ecma262/#sec-set.prototype.issubsetof
+$({ target: 'Set', proto: true, real: true, forced: INCORRECT }, {
+  isSubsetOf: isSubsetOf
+});