Upon programmatic window state changes, windowStateChange was fired
once in QWindow::setWindowStates and once when the visual state had
been changed by the window interface.
This patch adds if guards to ensure that the singal is fired only once.
It adds a corresponding autotest to tst_QWindow.
tst_QWidget::resizePropagation() is adapted to no longer expect double
signal emission.
Fixes: QTBUG-102478
Pick-to: 6.4 6.2
Change-Id: If093c0a883d76d8a676e4fab90db6b0676452267
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
52dcd47850