make QWindow::requestActivate() working in auto tests on Wayland

Since https://codereview.qt-project.org/c/qt/qtwayland/+/536495 , client: Announce platform support for WindowActivation . Then many auto tests will run QWindow::requestActivate() and follow up.

At least I have checked a few new failures in QTBUG-137020

• tst_QGuiApplication::focusObject(): https://github.com/qt/qtbase/blob/dev/tests/auto/gui/kernel/qguiapplication/tst_qguiapplication.cpp#L222
• tst_QApplication::activateDeactivateEvent(): https://github.com/qt/qtbase/blob/dev/tests/auto/widgets/kernel/qapplication/tst_qapplication.cpp#L1409

See also https://doc.qt.io/qt-6/qwindow.html#requestActivate