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/regexp-flags.js

@@ -0,0 +1,18 @@
+'use strict';
+var anObject = require('../internals/an-object');
+
+// `RegExp.prototype.flags` getter implementation
+// https://tc39.es/ecma262/#sec-get-regexp.prototype.flags
+module.exports = function () {
+  var that = anObject(this);
+  var result = '';
+  if (that.hasIndices) result += 'd';
+  if (that.global) result += 'g';
+  if (that.ignoreCase) result += 'i';
+  if (that.multiline) result += 'm';
+  if (that.dotAll) result += 's';
+  if (that.unicode) result += 'u';
+  if (that.unicodeSets) result += 'v';
+  if (that.sticky) result += 'y';
+  return result;
+};