Use sip-build and python3_add_library for Qt5/Qt6

[sloretz]

I'm playing around with an alternative to #143.
Requires ros/rosdistro#50338

If I understand correctly, and I'm not sure that I do, python_qt_binding uses a Python script sip_configure.py to produce a Makefile that produces a cPython extension.

#143 uses sip-build, but sets it up to use pip install to generate the bindings. It ends up creating a separate function build_sip_6_binding to use this new approach with a configurable pyproject.toml.in template downstream in qt_gui_core.

This PR uses sip-build and the CMake function python3_add_library to build a cPython extension instead. This PR allows using sip-build on both Qt5 and Qt6 bindings, though right now I've only tested it with Qt5 on Noble. I'll need to update the Python code like @ahcorde has in #143 to import from PyQt6.

I used Gemini 3.1 Pro to help make this PR

[sloretz]

After looking into this a bit, this is too much to pursue right now. I'm going to close this for now. Nevermind, realized what I was doing wrong