Support Qt6

[ahcorde]

This PR is related with this other one ros-visualization/qt_gui_core#293 in qt_gui_cpp.

It will set the required variables for shiboken6 and pyside6.

The file pyside_config.py was copied from https://github.com/pyside/pyside-setup/blob/dev/examples/utils/pyside_config.py

[mqcmd196]

+1

[mosfet80]

if qt6 is used, pyqt5 will still be used:

cmake/sip_configure.py:9:import PyQt5
cmake/sip_configure.py:10:from PyQt5 import QtCore
cmake/sip_configure.py:53: Get the extra SIP flags needed by the imported qt module, and locate PyQt5 sip install files.
cmake/sip_configure.py:73: candidate_sip_dirs.append(os.path.join(PyQt5.path[0], 'bindings'))
cmake/sip_configure.py:76: candidate_sip_dirs.append(os.path.join(sipconfig._pkg_config['default_sip_dir'], 'PyQt5'))
cmake/sip_configure.py:85: raise FileNotFoundError('The sip directory for PyQt5 could not be located. Please ensure' +
cmake/sip_configure.py:86: ' that PyQt5 is installed')
src/python_qt_binding/binding_helper.py:158: _named_import('PyQt5.%s' % module_name)
src/python_qt_binding/binding_helper.py:160: _named_optional_import('PyQt5.%s' % module_name)
src/python_qt_binding/binding_helper.py:169: import PyQt5.Qwt5
src/python_qt_binding/binding_helper.py:170: _register_binding_module('Qwt', PyQt5.Qwt5)
src/python_qt_binding/binding_helper.py:177: from PyQt5 import uic
src/python_qt_binding/binding_helper.py:180: import PyQt5.QtCore
src/python_qt_binding/binding_helper.py:181: return PyQt5.QtCore.PYQT_VERSION_STR