Add Louvain community detection algorithm #484

Job	Run time
posix-cmake-subdir (ubuntu-24.04)	1m 5s
macos (clang, 20)	8m 8s
windows_msvc_14_3 (msvc-14.3)	23m 3s
posix-cmake-subdir (ubuntu-22.04)	1m 19s
posix-cmake-install (ubuntu-24.04)	1m 43s
ubuntu (gcc-14, 17)	7m 12s
ubuntu (clang-19, 23)	10m 8s
macos (clang, 14)	5m 50s
posix-cmake-install (ubuntu-22.04)	1m 47s
ubuntu (clang-19, 14)	7m 33s
windows-cmake-subdir (windows-2025)	3m 23s
ubuntu (clang-19, 17)	7m 27s
posix-cmake-subdir (macos-14)	1m 30s
posix-cmake-install (macos-15)	2m 12s
macos (clang, 17)	6m 56s
posix-cmake-subdir (macos-15)	2m 1s
windows-cmake-subdir (windows-2022)	2m 52s
ubuntu (gcc-14, 20)	7m 44s
ubuntu (clang-19, 20)	9m 50s
windows-cmake-install (windows-2022)	3m 47s
ubuntu (gcc-14, 14)	6m 40s
ubuntu (gcc-14, 23)	9m 26s
posix-cmake-install (macos-14)	1m 47s
windows-cmake-install (windows-2025)	4m 0s
	2h 17m 23s

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