Fix failing mouseMovementProperties auto test on Windows and macOS

The view did not get all the movement events if the mouse was moved
onto the view after it had loaded the page. Fix this by placing the
mouse onto the view before setting the html content.

Task-number: QTBUG-66527
Change-Id: I6d6847d5215005fe9490250b5b4f0c01ce317c23
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>