Change fanout to scale by std::log rather than std::sqrt #2624

Job	Run time
macOS [UBSAN] [lmdb \| clang]	32m 31s
Linux [UBSAN] [lmdb \| clang]	38m 16s
macOS [ASAN] [lmdb \| clang]	29m 40s
Linux [ASAN] [lmdb \| clang]	38m 28s
macOS [TSAN] [lmdb \| clang]	32m 24s
Linux [ASAN_INT] [lmdb \| clang] (Errors Ignored)	40m 4s
macOS [UBSAN] [rocksdb \| clang]	41m 49s
Linux [TSAN] [lmdb \| clang]	40m 11s
macOS [ASAN] [rocksdb \| clang]	35m 6s
Linux [LEAK] [lmdb \| clang]	42m 12s
macOS [TSAN] [rocksdb \| clang]	55m 13s
Linux [UBSAN] [rocksdb \| clang]	48m 8s
Linux [ASAN] [rocksdb \| clang]	53m 0s
Linux [ASAN_INT] [rocksdb \| clang] (Errors Ignored)	57m 8s
Linux [LEAK] [rocksdb \| clang]	56m 29s
	10h 40m 39s

Provide feedback