Support for multiple levels per edge/area #227

Job	Run time
Get environment variables	1s
formatting	23s
build (macOS x86_64 Release, clang++, clang, Release, on, -stdlib=libc++, macos-13, macos-x86_64)	2m 39s
build (macOS arm64 Release, clang++, clang, Release, on, -stdlib=libc++, macos-14, macos-arm64)	2m 34s
build (GCC 12 Release, g++-12, gcc-12, Release, on, ubuntu-latest, linux)	1m 41s
build (GCC 12 Debug, g++-12, gcc-12, Debug, on, ubuntu-latest)	1m 52s
build (Clang 16 Release, clang++-16, clang-16, Release, on, -stdlib=libc++, -lc++abi, ubuntu-latest)	2m 27s
build (Clang Tidy, clang++-16, clang-16, Release, on, -stdlib=libc++, -lc++abi, true, ubuntu-latest)	2m 26s
build (Clang 16 Sanitizer, clang++-16, clang-16, Release, on, -fsanitize=address,undefined -fno-o...	2m 26s
	16m 29s

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