Destroy Qt5Frame after all events are received.
Update Qt5Object to use delayed destruction too.

Change-Id: I07c7251e097ad56f3616f325fdc394d00fec4f4f
Reviewed-on: https://gerrit.libreoffice.org/68316
Tested-by: Jenkins
Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>