Add Louvain community detection algorithm #497

Job	Run time
windows-cmake-install (windows-2025)	4m 32s
posix-cmake-subdir (ubuntu-22.04)	1m 27s
windows-cmake-subdir (windows-2025)	4m 24s
macos (clang, 20)	6m 18s
posix-cmake-install (macos-14)	2m 3s
windows-cmake-subdir (windows-2022)	2m 56s
posix-cmake-install (ubuntu-22.04)	1m 35s
macos (clang, 14)	8m 16s
ubuntu (gcc-14, 17)	8m 25s
windows_msvc_14_3 (msvc-14.3)	24m 58s
ubuntu (clang-19, 23)	10m 37s
posix-cmake-install (macos-15)	1m 54s
ubuntu (clang-19, 14)	6m 45s
ubuntu (gcc-14, 23)	8m 33s
posix-cmake-install (ubuntu-24.04)	1m 31s
ubuntu (clang-19, 20)	9m 22s
posix-cmake-subdir (macos-14)	1m 39s
windows-cmake-install (windows-2022)	4m 44s
ubuntu (gcc-14, 20)	8m 22s
posix-cmake-subdir (macos-15)	2m 41s
ubuntu (gcc-14, 14)	6m 37s
macos (clang, 17)	8m 51s
ubuntu (clang-19, 17)	8m 29s
posix-cmake-subdir (ubuntu-24.04)	1m 39s
	2h 26m 38s

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