Tests for `frontier_scan` class #2595

Job	Run time
Linux [UBSAN] [lmdb \| clang]	42m 3s
macOS [UBSAN] [lmdb \| clang]	31m 52s
macOS [ASAN] [lmdb \| clang]	25m 16s
Linux [ASAN] [lmdb \| clang]	41m 39s
macOS [TSAN] [lmdb \| clang]	31m 4s
Linux [ASAN_INT] [lmdb \| clang] (Errors Ignored)	39m 19s
macOS [UBSAN] [rocksdb \| clang]	40m 48s
Linux [TSAN] [lmdb \| clang]	43m 7s
macOS [ASAN] [rocksdb \| clang]	37m 52s
Linux [LEAK] [lmdb \| clang]	38m 29s
macOS [TSAN] [rocksdb \| clang]	47m 2s
Linux [UBSAN] [rocksdb \| clang]	51m 23s
Linux [ASAN] [rocksdb \| clang]	52m 38s
Linux [ASAN_INT] [rocksdb \| clang] (Errors Ignored)	54m 57s
Linux [LEAK] [rocksdb \| clang]	53m 16s
	10h 30m 45s

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