Use the ChatBar Component for new thread messages

![image](/uploads/a24dea919e7f165d602991659f517c22/image.png){width=148 height=210}

Note: there is still an issue where after starting a new thread the threaded messages only appear after a restart as the root event needs re-downloading from the server to get the thread info added. My plan is to tackle this next.

src/chatbarcache.h

@@ -195,7 +195,7 @@ public:
 Q_SIGNALS:
     void textChanged();
     void relationIdChanged(const QString &oldEventId, const QString &newEventId);
-    void threadIdChanged();
+    void threadIdChanged(const QString &oldThreadId, const QString &newThreadId);
     void attachmentPathChanged();
 
 private: