0.5.0

Breaking

• added Config::flush_worker to configure maximum amount of parallel memtable flushes
• added Keyspace::persist_paranoid, which uses fsync, compared to Keyspace::persist which uses fdatasync
• added Keyspace::list_partitions
• added axum-kv example
• upgraded lsm-tree to 0.5.0
• internal refactors
• finished repo restructuring