Refactor: homogenize code surrounding VNF converter #169

Job	Run time
Build sdist and set version	1m 21s
build-cpp-test-macos (debug)	3m 18s
build-cpp-test-linux (debug, gcc)	5m 6s
build-cpp-test-windows (debug, msvc)	6m 21s
build-cpp-test-macos (release)	2m 57s
build-cpp-test-linux (debug, clang)	2m 44s
build-cpp-test-windows (debug, clang-cl)	5m 46s
build-cpp-test-linux (release, gcc)	6m 33s
build-cpp-test-windows (release, msvc)	6m 30s
build-cpp-test-linux (release, clang)	5m 11s
Build and test in Conda (ubuntu)	1m 8s
build-cpp-test-windows (release, clang-cl)	9m 6s
Build and test in Conda (windows)	3m 36s
build-and-test-python (linux-x64)	5m 10s
build-and-test-python (linux-aarch64)	11m 34s
build-and-test-python (macos)	3m 39s
build-and-test-python (windows)	13m 8s
publish-wheels	5s
	1h 33m 13s

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