QObjects must be deleted if the QCoreApplication is being destroyed.
This was previously done by implementing custom code in qtbase and
other modules. So unify it and introduce a Q_APPLICATION_STATIC,
based on the Q_GLOBAL_STATIC, which centralises the logic.
Since we still have a few remaining living QObjects,
this comes in handy to fix those as well.
Task-number: QTBUG-84234
Change-Id: I3040a2280ff56291f2b1c39948c06a23597865c4
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>