[desktop] More qt_common reorganization (#3916)

Ported from QML branch.

Main "big" change is that EmuThread is now a shared state in QtCommon,
not individually managed/passed around by GRenderWindow and MainWindow.

Signed-off-by: crueter <crueter@eden-emu.dev>
Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3916
Reviewed-by: Lizzie <lizzie@eden-emu.dev>
Reviewed-by: MaranBr <maranbr@eden-emu.dev>

src/qt_common/util/game.h

@@ -69,6 +69,14 @@ void CreateShortcut(const std::string& game_path, const u64 program_id,
 std::string GetShortcutPath(ShortcutTarget target);
 void CreateHomeMenuShortcut(ShortcutTarget target);
 
+/**
+ * Saves a windows icon to a file
+ * @param path The icons path
+ * @param image The image to save
+ * @return bool If the operation succeeded
+ */
+[[nodiscard]] bool SaveIconToFile(const std::filesystem::path& icon_path, const QImage& image);
+
 } // namespace QtCommon::Game
 
 #endif // QT_GAME_UTIL_H