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/indexed-object.js

@@ -0,0 +1,16 @@
+'use strict';
+var uncurryThis = require('../internals/function-uncurry-this');
+var fails = require('../internals/fails');
+var classof = require('../internals/classof-raw');
+
+var $Object = Object;
+var split = uncurryThis(''.split);
+
+// fallback for non-array-like ES3 and non-enumerable old V8 strings
+module.exports = fails(function () {
+  // throws an error in rhino, see https://github.com/mozilla/rhino/issues/346
+  // eslint-disable-next-line no-prototype-builtins -- safe
+  return !$Object('z').propertyIsEnumerable(0);
+}) ? function (it) {
+  return classof(it) === 'String' ? split(it, '') : $Object(it);
+} : $Object;