Reduce layout shift when loading mutual rooms in user profiles

Instead of making the visibility of this section in user profiles
dependent on the model, its now checking if you can check mutual rooms
and using a busy indicator. There's also a label for when you have no
rooms in common, which is a rare case (for example, banned or left
users.)

src/app/models/commonroomsmodel.h

@@ -21,6 +21,7 @@ class CommonRoomsModel : public QAbstractListModel
     Q_PROPERTY(NeoChatConnection *connection WRITE setConnection READ connection NOTIFY connectionChanged REQUIRED)
     Q_PROPERTY(QString userId WRITE setUserId READ userId NOTIFY userIdChanged REQUIRED)
     Q_PROPERTY(int count READ rowCount NOTIFY countChanged)
+    Q_PROPERTY(bool loading READ loading NOTIFY loadingChanged)
 
 public:
     enum Roles {
@@ -43,10 +44,13 @@ public:
 
     QHash<int, QByteArray> roleNames() const override;
 
+    bool loading() const;
+
 Q_SIGNALS:
     void connectionChanged();
     void userIdChanged();
     void countChanged();
+    void loadingChanged();
 
 private:
     void reload();
@@ -54,4 +58,5 @@ private:
     QPointer<NeoChatConnection> m_connection;
     QString m_userId;
     QList<QString> m_commonRooms;
+    bool m_loading = false;
 };