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/set-is-subset-of.js

@@ -0,0 +1,16 @@
+'use strict';
+var aSet = require('../internals/a-set');
+var size = require('../internals/set-size');
+var iterate = require('../internals/set-iterate');
+var getSetRecord = require('../internals/get-set-record');
+
+// `Set.prototype.isSubsetOf` method
+// https://tc39.es/ecma262/#sec-set.prototype.issubsetof
+module.exports = function isSubsetOf(other) {
+  var O = aSet(this);
+  var otherRec = getSetRecord(other);
+  if (size(O) > otherRec.size) return false;
+  return iterate(O, function (e) {
+    if (!otherRec.includes(e)) return false;
+  }, true) !== false;
+};