Fix database iterator-transaction lifetimes #2194

Job	Run time
Linux [UBSAN] [lmdb \| clang]	38m 42s
Linux [ASAN] [lmdb \| clang]	40m 22s
Linux [ASAN_INT] [lmdb \| clang] (Errors Ignored)	40m 34s
Linux [TSAN] [lmdb \| clang]	41m 9s
macOS [UBSAN] [lmdb \| clang]	32m 57s
Linux [LEAK] [lmdb \| clang] (Errors Ignored)	40m 16s
macOS [ASAN] [lmdb \| clang]	30m 30s
Linux [UBSAN] [rocksdb \| clang]	51m 15s
macOS [TSAN] [lmdb \| clang]	34m 37s
Linux [ASAN] [rocksdb \| clang]	56m 55s
macOS [UBSAN] [rocksdb \| clang]	43m 30s
Linux [ASAN_INT] [rocksdb \| clang] (Errors Ignored)	59m 1s
macOS [ASAN] [rocksdb \| clang]	42m 43s
Linux [LEAK] [rocksdb \| clang] (Errors Ignored)	57m 58s
macOS [TSAN] [rocksdb \| clang]	53m 35s
	11h 4m 4s

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