Add Qt::AA_QtQuickDontUseDefaultSizePolicy

This flag should be set in order to opt out of that Qt Quick Layouts
takes implicit (built-in) size policies into account, a feature that was
introduced in Qt 6.7

Task-number: QTBUG-117597
Change-Id: I206cd61534b2103b2c3a9b4abc97fec8c88799d1
Reviewed-by: Santhosh Kumar <santhosh.kumar.selvaraj@qt.io>
(cherry picked from commit 4ae537e67c99160f5dcac99f40d03a7921456556)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/corelib/global/qnamespace.h

@@ -422,7 +422,7 @@ namespace Qt {
     enum ApplicationAttribute
     {
         // AA_ImmediateWidgetCreation = 0,
-        // AA_MSWindowsUseDirect3DByDefault = 1,
+        AA_QtQuickDontUseDefaultSizePolicy = 1,
         AA_DontShowIconsInMenus = 2,
         AA_NativeWindows = 3,
         AA_DontCreateNativeWidgetSiblings = 4,

src/corelib/global/qnamespace.qdoc

@@ -84,6 +84,11 @@
     QCoreApplication::testAttribute().
 
 
+    \value [since 6.7] AA_QtQuickDontUseDefaultSizePolicy Qt Quick Layouts won't use the built-in
+           size policy of \l Item. This restores previous behavior where all items were fixed size
+           by default. Size policy can be customized by explicitly setting
+           \l{Layout::fillWidth}{Layout.fillWidth} or \l{Layout::fillHeight}{Layout.fillHeight}.
+
     \value AA_DontShowIconsInMenus Actions with the Icon property won't be
            shown in any menus unless specifically set by the
            QAction::iconVisibleInMenu property.