QTableView auto-section-resize broken since Qt 6.9

It seems that as a result of 9e3a96189d9db8a458e65cd5078509afe7a160db, the sections of a QTableView are no longer automatically resizing when their size hint is changed before calling QAbstractItemView::scheduleDelayedItemsLayout and optionally QAbstractItemView::executeDelayedItemsLayout.

Some debugging revealed that this is likely due to QHeaderViewPrivate::hasAutoResizeSections returning false since its contentsSections value remains on 0 rather than reflecting the number of actual sections (since it now only updates QHeaderViewPrivate::countInNoSectionItemsMode). This in turn causes QHeaderView::updateGeometries not to call QHeaderViewPrivate::doDelayedResizeSections, which means that eventually in executePostedResize the delayedResize.isActive() check fails.

I don't have a small example to reproduce this problem, but I do have an application which is now broken on Arch Linux and Fedora since they've already updated to Qt 6.9 and users are now running into this issue: https://github.com/mapeditor/tiled/issues/4191