CLN: refactor C++/pybind11 single variables to structs #421

Job	Run time
Python 3.9 on ubuntu-latest-manylinux_x86_64	3m 49s
Python 3.9 on windows-latest-win_amd64	7m 37s
Python 3.9 on macos-13-macosx_x86_64	5m 52s
Python 3.9 on macos-latest-macosx_arm64	6m 35s
Python 3.10 on ubuntu-latest-manylinux_x86_64	3m 54s
Python 3.10 on windows-latest-win_amd64	6m 52s
Python 3.10 on macos-13-macosx_x86_64	6m 21s
Python 3.10 on macos-latest-macosx_arm64	5m 24s
Python 3.11 on ubuntu-latest-manylinux_x86_64	3m 51s
Python 3.11 on windows-latest-win_amd64	7m 15s
Python 3.11 on macos-13-macosx_x86_64	5m 40s
Python 3.11 on macos-latest-macosx_arm64	3m 7s
Python 3.12 on ubuntu-latest-manylinux_x86_64	3m 56s
Python 3.12 on windows-latest-win_amd64	6m 42s
Python 3.12 on macos-13-macosx_x86_64	4m 22s
Python 3.12 on macos-latest-macosx_arm64	4m 7s
publish	0s
	1h 25m 24s

Provide feedback