Migration to QT6

[pktiuk]

QT6 is mature enough to start efforts of porting AntiMicroX to it.
It is also needed for updating runtime for flatpak (see: flathub/io.github.antimicrox.antimicrox#11)

Tasks to do:

• Deal with deprecated APIs
  • Fix deprecation warnings #318
  • QList::toSet is deprecated #425
  • QFontMetrics::width() is deprecated #426
  • QStringList QString::split in common.cpp
  • QRect QDesktopWidget::screenGeometry in event.cpp
  • QWheelEvent::orientation()
  • Remove QDesktopWidget Class link

Others

• Update CMake to handle QT6 chore: Add support for QT6 #959
• Add CI configs using QT6

Resources:

• https://doc.qt.io/qt-6/portingguide.html
• https://www.qt.io/blog/porting-from-qt-5-to-qt-6-using-qt5compat-library
• https://doc.qt.io/qt-6/cmake-qt5-and-qt6-compatibility.html
• https://doc.qt.io/qt-6/cmake-get-started.html

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