None of these users require C++20 constexpr or C++23 noexcept, the
only remaining difference between std::exchange and qExchange.
This leaves a single qExchange() user, in QScopedValueRollback, that
requires the constexpr version, only available from C++20, and thus
remains unported.
Task-number: QTBUG-99313
Change-Id: Iea46f6ed61d6bd8a5b2fd9d9ec4d70c980b443a2
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>