CLN: refactor C++/pybind11 single variables to structs #424

Job	Run time
Python 3.9 on ubuntu-latest-manylinux_x86_64	3m 43s
Python 3.9 on windows-latest-win_amd64	9m 2s
Python 3.9 on macos-13-macosx_x86_64	8m 5s
Python 3.9 on macos-latest-macosx_arm64	5m 34s
Python 3.10 on ubuntu-latest-manylinux_x86_64	3m 59s
Python 3.10 on windows-latest-win_amd64	3m 14s
Python 3.10 on macos-13-macosx_x86_64	6m 28s
Python 3.10 on macos-latest-macosx_arm64	4m 27s
Python 3.11 on ubuntu-latest-manylinux_x86_64	3m 46s
Python 3.11 on windows-latest-win_amd64	2m 30s
Python 3.11 on macos-13-macosx_x86_64	7m 11s
Python 3.11 on macos-latest-macosx_arm64	3m 21s
Python 3.12 on ubuntu-latest-manylinux_x86_64	4m 4s
Python 3.12 on windows-latest-win_amd64	1m 51s
Python 3.12 on macos-13-macosx_x86_64	8m 59s
Python 3.12 on macos-latest-macosx_arm64	2m 55s
publish	0s
	1h 19m 9s

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