These options, inspired by Nethermind and general internet wisdom, bring
the database size down to 2/3 without affecting throughput. In theory,
they should also bring down memory usage and/or make more efficient use
of whatever memory is already assigned to rocksdb but this needs
verification in a longer test at synced-mainnet sizes.
In the meantime, they make testing easier by removing some noise that
the profiler says are bad, such as excessive SkipList access (countered
by bloom filters).
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