DirectShow: Fix crash when camera is being destroyed

If a camera is going to be destroyed, a service plugin releases media service,
(which releases ds camera session) and might call CoUninitialize.
This leads to a crash when DirectShowSampleGrabber is destroyed after
releasing the camera.
Added a fix to release the sample grabber together with camera session.

Task-number: QTBUG-73461
Change-Id: I8e518d0242d983c8d2bb00c30ad87c7e8e1e2c93
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>