Differentiate normal and final generator thread roles (#4838) #2629

Job	Run time
macOS [UBSAN] [lmdb \| clang]	36m 33s
Linux [UBSAN] [lmdb \| clang]	42m 12s
macOS [ASAN] [lmdb \| clang]	29m 37s
Linux [ASAN] [lmdb \| clang]	41m 3s
macOS [TSAN] [lmdb \| clang]	32m 59s
Linux [ASAN_INT] [lmdb \| clang] (Errors Ignored)	40m 58s
macOS [UBSAN] [rocksdb \| clang]	42m 55s
Linux [TSAN] [lmdb \| clang]	41m 9s
macOS [ASAN] [rocksdb \| clang]	37m 4s
Linux [LEAK] [lmdb \| clang]	40m 30s
macOS [TSAN] [rocksdb \| clang]	51m 53s
Linux [UBSAN] [rocksdb \| clang]	49m 3s
Linux [ASAN] [rocksdb \| clang]	54m 55s
Linux [ASAN_INT] [rocksdb \| clang] (Errors Ignored)	57m 29s
Linux [LEAK] [rocksdb \| clang]	53m 20s
	10h 51m 40s

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