Add a test for embedding Qt windows into foreign windows.
Complements the existing "foreignwindows" test (which embeds
foreign windows into Qt).
The test has a simple UI based on QRasterWindow allowing
for checking events and geometries.
Task-number: QTBUG-41186
Change-Id: Ie62a3e250ca666e2fa5c2e3ef37ef0654829397c
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
