Menu: Don't create platform item for QQuickMenuItemContainers

They don't have any QPA counterpart as they're just plain containers.
This also removes that "Menu does not contain the item to be removed"
warning on Mac.

Task-Number: QTBUG-32197
Change-Id: I06e08817194c2e3ad3efd7ded193bfac9d3a1948
Reviewed-by: Jens Bache-Wiig <jens.bache-wiig@digia.com>
Fixed: Regression in key navigation on TableView

It turns out the currentIndex/CurrentRow was updated but the selection,
was ignored for the last row in a TableView.

[ChangeLog][Qt Quick Controls][Fixed: TableView regression where
the last row in a TableView could not be selected by keyboard.]

Task-number: QTBUG-35572
Change-Id: Ifdf11f665733dd63ba56e12fe0dabdd7932a4ab9
Reviewed-by: Caroline Chao <caroline.chao@digia.com>
Merge remote-tracking branch 'origin/stable' into dev

Change-Id: Ic5df7eed17a305e6ebb7235d30467124269ea751