Terminal: Move color mapping to widget

This allows us to easily update the view when the colors are changed
in the settings.

Change-Id: I0b4f150b4fc9cec9aee2796d63f2395e05ce70df
Reviewed-by: Cristian Adam <cristian.adam@qt.io>

src/plugins/terminal/terminalwidget.h

@@ -166,6 +166,8 @@ protected:
 
     void configBlinkTimer();
 
+    QColor toQColor(std::variant<int, QColor> color) const;
+
 private:
     std::unique_ptr<Utils::QtcProcess> m_process;
     std::unique_ptr<Internal::TerminalSurface> m_surface;