Support Qt6

[ahcorde]

Related with ros2/ros2#1798

I'm getting this error:

RosPluginlibPluginProvider::load_explicit_type(rqt_image_view/ImageView) could not load library (Failed to load library /home/ahcorde/ros2_rolling/install_qt6/lib/rqt_image_view/librqt_image_view.so. Make sure that you are calling the PLUGINLIB_EXPORT_CLASS macro in the library code, and that names are consistent between this macro and your XML. Error string: Could not load library dlopen error: /home/ahcorde/ros2_rolling/install_qt6/lib/rqt_image_view/librqt_image_view.so: undefined symbol: _ZN6QFrame16staticMetaObjectE, at /home/ahcorde/ros2_rolling/src/ros2/rcutils/src/shared_library.c:96)
PluginManager._load_plugin_restore()
PluginManager._load_plugin() could not load plugin "['rqt_image_view/ImageView']": RosPluginlibPluginProvider.load() could not load plugin "['rqt_image_view/ImageView']"
Warning: class_loader.ClassLoader: SEVERE WARNING!!! Attempting to unload library while objects created by this loader exist in the heap! You should delete your objects before attempting to unload the library or destroying the ClassLoader. The library will NOT be unloaded.
         at line 127 in /home/ahcorde/ros2_rolling/src/ros/class_loader/src/class_loader.cpp

[ahcorde]

Issues is alread fixed

FYI @asymingt