migrate_database_lmdb_to_rocksdb improvements #1990

Job	Run time
macOS [UBSAN] [lmdb \| clang]	36m 21s
Linux [UBSAN] [lmdb \| clang]	38m 2s
macOS [ASAN] [lmdb \| clang]	27m 41s
Linux [ASAN] [lmdb \| clang]	40m 21s
macOS [TSAN] [lmdb \| clang]	30m 40s
Linux [ASAN_INT] [lmdb \| clang] (Errors Ignored)	38m 50s
macOS [UBSAN] [rocksdb \| clang]	39m 12s
Linux [TSAN] [lmdb \| clang]	41m 37s
macOS [ASAN] [rocksdb \| clang]	35m 42s
Linux [LEAK] [lmdb \| clang] (Errors Ignored)	41m 27s
macOS [TSAN] [rocksdb \| clang]	47m 15s
Linux [UBSAN] [rocksdb \| clang]	47m 7s
Linux [ASAN] [rocksdb \| clang]	49m 7s
Linux [ASAN_INT] [rocksdb \| clang] (Errors Ignored)	49m 14s
Linux [LEAK] [rocksdb \| clang] (Errors Ignored)	48m 13s
	10h 10m 49s

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