Move storageview example into tests/manual

The code is mostly an implementation of a model based on QStorageInfo,
shown in an otherwise uninteresting tree view.

Pick-to: 6.5 6.6
Change-Id: Id6ce70d71ddc9bcd6e82a9ee12f5e1af159eac7a
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

examples/widgets/itemviews/CMakeLists.txt

@@ -18,7 +18,6 @@ qt_internal_add_example(simplewidgetmapper)
 qt_internal_add_example(spinboxdelegate)
 qt_internal_add_example(spreadsheet)
 qt_internal_add_example(stardelegate)
-qt_internal_add_example(storageview)
 if(QT_FEATURE_draganddrop)
     qt_internal_add_example(puzzle)
 endif()

examples/widgets/itemviews/itemviews.pro

@@ -17,7 +17,6 @@ SUBDIRS       = addressbook \
                 simplewidgetmapper \
                 spinboxdelegate \
                 spreadsheet \
-                stardelegate \
-                storageview
+                stardelegate
 !qtConfig(draganddrop): SUBDIRS -= puzzle
 !qtHaveModule(xml): SUBDIRS -= simpledommodel