ProjectExplorer: Introduce TextDisplay for simple display tasks

That's effectively a beefed-up TextDisplay previously used only in
Incredibuild.

Change-Id: I0cedef24cede8b8513e80b64f589abe62a68814e
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/incredibuild/commandbuilderaspect.h

@@ -52,17 +52,5 @@ private:
     class CommandBuilderAspectPrivate *d = nullptr;
 };
 
-class TextDisplay final : public ProjectExplorer::ProjectConfigurationAspect
-{
-public:
-    TextDisplay(const QString &message) : m_message(message) {}
-
-private:
-    void addToLayout(ProjectExplorer::LayoutBuilder &builder) final;
-
-    QString m_message;
-    QPointer<QLabel> m_label;
-};
-
 } // namespace Internal
 } // namespace IncrediBuild