QmlProfiler: De-pimpl QmlProfilerViewManager

The change is purely mechanical. QmlProfilerViewManager
is an internal class, not even extra #includes are needed.

Change-Id: Ia28b3a90c8c7dfeb1eb2510b4030c566bc264a46
Reviewed-by: Kai Koehne <kai.koehne@qt.io>
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>