Revert "Utils: Remove the text option for LayoutItem"

This reverts commit 5154e1eb02.

For some yet unknown reason, this renders the whole sublayout read-only.

Change-Id: Ide1587382392a57643bed1b3cdd7d8987dbdab57
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/libs/utils/layoutbuilder.h

@@ -62,6 +62,7 @@ public:
         QLayout *layout = nullptr;
         QWidget *widget = nullptr;
         BaseAspect *aspect = nullptr;
+        QString text;
         int span = 1;
         Qt::Alignment align;
     };