Disallow database operations on network IO threads #2478

Job	Run time
Linux [UBSAN] [lmdb \| clang]	38m 31s
macOS [UBSAN] [lmdb \| clang]	40m 47s
Linux [ASAN] [lmdb \| clang]	37m 53s
macOS [ASAN] [lmdb \| clang]	34m 16s
Linux [ASAN_INT] [lmdb \| clang] (Errors Ignored)	41m 6s
macOS [TSAN] [lmdb \| clang]	25m 13s
Linux [TSAN] [lmdb \| clang]	42m 5s
macOS [UBSAN] [rocksdb \| clang]	45m 12s
Linux [LEAK] [lmdb \| clang]	37m 42s
macOS [ASAN] [rocksdb \| clang]	40m 44s
Linux [UBSAN] [rocksdb \| clang]	46m 12s
macOS [TSAN] [rocksdb \| clang]	55m 2s
Linux [ASAN] [rocksdb \| clang]	53m 35s
Linux [ASAN_INT] [rocksdb \| clang] (Errors Ignored)	55m 19s
Linux [LEAK] [rocksdb \| clang]	54m 15s
	10h 47m 52s

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