qCDebug(lcDeleteLater) is very late in some cases

Commit c3a2b9f35a9a12ff3c6f5f0d11844de161b47c2a added categorised logging to the QObject::deleterLater feature. Unfortunately, some of the categorised logging in question happen at very inopportune moments: very late in a thread's exit or in the application's exit. This was first noticed in QTBUG-129927.

I believe this is the worst offender:

        d->threadState = QThreadPrivate::Finishing;
        locker.unlock();
        emit thr->finished(QThread::QPrivateSignal());
        qCDebug(lcDeleteLater) << "Sending deferred delete events as part of finishing thread" << thr;
        QCoreApplication::sendPostedEvents(nullptr, QEvent::DeferredDelete);

For threads started with QThread, this function is run right after the user's code returns from QThread::run() (except for Qt 6.4-6.8, where it was run later on some platforms, but that was changed back to the historical time with the commit that fixed QTBUG-129927). For adopted threads, this function is runs late, when either PThread runs the pthread_key_t callbacks or the C++ runtime runs the non-trivial destructors.

Specifically, do note the thread that executed main() is an adopted thread.

One crash was noticed in tests/auto/widgets/kernel/qapplication/modal/base.cpp, which calls ::exit() from a QTimer. I believe I fixed that one in QThread itself. The one I can't fix because I can't reproduce is:

$ ctest --test-dir $objdir -R test_add_binary_resources_delayed_file --output-on-failure
...
Running test command: "/Users/tjmaciei/obj/qt/qt6/qtbase/tests/auto/cmake/test_add_binary_resources_delayed_file/test_add_binary_resources_delayed_file"
Test command failed: /Users/tjmaciei/obj/qt/qt6/qtbase/tests/auto/cmake/test_add_binary_resources_delayed_file/test_add_binary_resources_delayed_file
[4223500.427] (9701 36767941)(unknown): ASSERT failure in Type &QtGlobalStatic::Impl<QtGlobalStatic::Holder<(anonymous namespace)::Q_QGS_defaultLocalePrivate, (anonymous namespace)::Q_QGS_defaultLocalePrivate>>::operator*() const [Holder = QtGlobalStatic::Holder<(anonymous namespace)::Q_QGS_defaultLocalePrivate, (anonymous namespace)::Q_QGS_defaultLocalePrivate>]: "The global static was used after being destroyed", file /Users/tjmaciei/src/qt/qt6/qtbase/src/corelib/global/qglobalstatic.h, line 136