Use start/stop pattern in `block_processor` #1337

Job	Run time
macOS [UBSAN] [lmdb \| clang]	31m 36s
Linux [UBSAN] [lmdb \| clang]	36m 47s
macOS [ASAN] [lmdb \| clang]	26m 32s
Linux [ASAN] [lmdb \| clang]	37m 47s
macOS [TSAN] [lmdb \| clang] (Errors Ignored)	30m 2s
Linux [ASAN_INT] [lmdb \| clang] (Errors Ignored)	39m 56s
macOS [UBSAN] [rocksdb \| clang]	38m 52s
macOS [ASAN] [rocksdb \| clang]	41m 25s
Linux [TSAN] [lmdb \| clang] (Errors Ignored)	39m 5s
macOS [TSAN] [rocksdb \| clang] (Errors Ignored)	47m 39s
Linux [LEAK] [lmdb \| clang] (Errors Ignored)	36m 8s
Linux [UBSAN] [rocksdb \| clang]	44m 46s
Linux [ASAN] [rocksdb \| clang]	46m 52s
Linux [ASAN_INT] [rocksdb \| clang] (Errors Ignored)	47m 13s
Linux [TSAN] [rocksdb \| clang] (Errors Ignored)	1h 33m 31s
Linux [LEAK] [rocksdb \| clang] (Errors Ignored)	49m 32s
	11h 27m 43s

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