addition of unified memtable config support, object store column family config fields, extended database statistics (unified memtable, object store, local cache, replica mode), iterator key_value combined access method, promote_to_primary replica promotion, and tdb_err_readonly error code; updated ffi struct definitions to align with latest tidesdb db.h; added 6 new tests covering all new features; bumped version to 0.5.7 · tidesdb/tidesdb-lua@db7ef47