Use batch event for background backlog scan #2365

Job	Run time
Linux [UBSAN] [lmdb \| clang]	37m 16s
macOS [UBSAN] [lmdb \| clang]	37m 4s
Linux [ASAN] [lmdb \| clang]	38m 12s
macOS [ASAN] [lmdb \| clang]	28m 33s
Linux [ASAN_INT] [lmdb \| clang] (Errors Ignored)	41m 10s
macOS [TSAN] [lmdb \| clang]	33m 44s
Linux [TSAN] [lmdb \| clang]	39m 14s
macOS [UBSAN] [rocksdb \| clang]	41m 32s
Linux [LEAK] [lmdb \| clang]	38m 16s
macOS [ASAN] [rocksdb \| clang]	39m 43s
Linux [UBSAN] [rocksdb \| clang]	48m 46s
macOS [TSAN] [rocksdb \| clang]	50m 28s
Linux [ASAN] [rocksdb \| clang]	54m 12s
Linux [ASAN_INT] [rocksdb \| clang] (Errors Ignored)	54m 58s
Linux [LEAK] [rocksdb \| clang]	54m 32s
	10h 37m 40s

Provide feedback