Refactor threads

The focus here is to make threads use the standard message content system rather than having a special implementation.

To achieve this the threadroot content model will now get a thread body component which will visualise the thread model with all the other messages. The latest message in the thread will then just ask for the thread root content model and show that.

Note: in order to stop a cyclical dependency with MessageComponentChooser and new base version has been added which is just missing ThreadBodyComponent and and the main version is now inherited from that with ThreadBodyComponent added.

src/models/messagecontentmodel.h

@@ -91,6 +91,8 @@ public:
      */
     [[nodiscard]] QHash<int, QByteArray> roleNames() const override;
 
+    static QHash<int, QByteArray> roleNamesStatic();
+
     /**
      * @brief Close the link preview at the given index.
      *