IWYU incorrect header suggestions

Header support for IWYU (include-what-you-use) was added with https://bugreports.qt.io/browse/QTBUG-119505

It has a number of issues compared to using 6.6.3 with the iwyu-mapgen-qt.py tool https://raw.githubusercontent.com/include-what-you-use/include-what-you-use/clang_13/mapgen/iwyu-mapgen-qt.py

• Code using QStringList that includes <QStringList> is recommended to remove that and use <qcontainerfwd.h>
• <qlist.h> is recommended for QList instead of <QList>
• <qtclasshelpermacros.h> is recommended for Q_DISABLE_COPY instead of <QObject>
• <qtmetamacros.h> is recommended for Q_OBJECT instead of <QObject>
• <QtCore/qobjectdefs.h> is recommended when using QObject::connect() with function pointers
• <qguiapplication.h> is recommended when qApp is used, even though <QCoreApplication> is included
• <qnamespace.h> is recommended for Qt::QueuedConnection instead of <Qt>

Using the IWYU iwyu-mapgen-qt.py tool to generate a mapping file with 6.6.3 fixes the above.

See the attached sample app, iwyu-sample.zip.

For 6.7.0 it was configured as follows:

$ mkdir build
$ CC="clang" CXX="clang++" cmake -S . -B build -DCMAKE_CXX_INCLUDE_WHAT_YOU_USE="/usr/bin/iwyu;-Xiwyu;--cxx17ns" --install-prefix /usr/local/Qt/6.7.0/gcc_64/
$ cmake --build build

IWYU output is attached as iwyu-6.7.0.log

 For 6.6.3 with iwyu-mapgen-qt.py, it was configured as follows:

$ curl -o "build/iwyu-mapgen-qt.py" https://raw.githubusercontent.com/include-what-you-use/include-what-you-use/clang_13/mapgen/iwyu-mapgen-qt.py
$ python3 "build/iwyu-mapgen-qt.py" /usr/local/Qt/6.6.3/gcc_64/include > "build/qt6.6.3.imp"
$ CC="clang" CXX="clang++" cmake -S . -B build -DCMAKE_CXX_INCLUDE_WHAT_YOU_USE="/usr/bin/iwyu;-Xiwyu;--cxx17ns;-Xiwyu;--mapping_file=$PWD/build/qt6.6.3.imp" --install-prefix /usr/local/Qt/6.6.3/gcc_64/
$ cmake --build build

IWYU output is attached as iwyu-6.6.3.log