Use vector-of-structs of preds/semi for Lengauer-Tarjan #339

Job	Run time
macos (clang)	10m 54s
posix-cmake-install (ubuntu-20.04)	1m 37s
ubuntu-focal (g++-9)	19m 40s
posix-cmake-install (ubuntu-22.04)	1m 27s
posix-cmake-subdir (ubuntu-20.04)	1m 2s
windows_msvc_14_2 (msvc-14.2)	23m 12s
ubuntu-focal (clang++-10)	17m 45s
posix-cmake-install (ubuntu-24.04)	1m 23s
posix-cmake-subdir (ubuntu-22.04)	1m 4s
posix-cmake-install (macos-13)	2m 43s
posix-cmake-subdir (ubuntu-24.04)	1m 4s
windows_msvc_14_3 (msvc-14.3)	24m 8s
posix-cmake-install (macos-14)	1m 28s
windows-cmake-install (windows-2019)	3m 36s
posix-cmake-subdir (macos-13)	2m 14s
posix-cmake-install (macos-15)	1m 34s
windows-cmake-install (windows-2022)	4m 45s
posix-cmake-subdir (macos-14)	1m 16s
windows-cmake-subdir (windows-2019)	2m 45s
posix-cmake-subdir (macos-15)	1m 38s
windows-cmake-subdir (windows-2022)	2m 56s
	2h 8m 11s

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