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/internals/object-to-string.js

@@ -0,0 +1,9 @@
+'use strict';
+var TO_STRING_TAG_SUPPORT = require('../internals/to-string-tag-support');
+var classof = require('../internals/classof');
+
+// `Object.prototype.toString` method implementation
+// https://tc39.es/ecma262/#sec-object.prototype.tostring
+module.exports = TO_STRING_TAG_SUPPORT ? {}.toString : function toString() {
+  return '[object ' + classof(this) + ']';
+};