Decide on exception handling in Qt::endPropertyUpdateGroup()

Gerrit discussion: https://codereview.qt-project.org/c/qt/qtbase/+/458459/comments/fa6a4318_f96c2421

While adding a RAII class around Qt::begin/endPropertyUpdateGroup() (QTBUG-110710), this author observed that Qt::endPropertyUpdateGroup() can throw exceptions (originally thrown from evaluating bindings or calling notifications), which causes a RAII'ed endPropertyUpdateGroup() to std::terminate() when called, as RAII classes are supposed to be, from stack unwinding.

This makes the RAII wrapper kinda useless.

This ticket is here to remember to decide what to do in this case and implement it accordingly.

Remember to remove and/or amend the documentation of QScopedPropertyUpdateGroup accrodingly.