Updating Appleseed: Python 3 and Dependencies

The goal of this project is to update the Python codebase for Appleseed from Python 2 to Python 3 and update the PyQT code and GUI to PyQT6. This update is necessary to ensure that Appleseed continues to function correctly and avoid potential issues that may arise due to Python 2's deprecation. The project will include updating the Boost C++ Libraries to the latest version and ensuring compatibility with other dependencies, including OpenEXR, OIIO, Embree, and Qt. Updating Appleseed to Python 3 may affect some of its dependencies, including Boost, PySide/PyQT, PIL, and other Python dependencies. Overall, this project will help ensure the long-term sustainability of Appleseed by modernizing the codebase and improving the user experience.