refactor: better interfaces, open cartridge API

sbroad-cartridge/src/api.rs

sbroad-cartridge/src/api/calculate_bucket_id.rs

sbroad-cartridge/src/api/exec_query.rs

sbroad-cartridge/src/api/invalidate_cached_schema.rs

sbroad-cartridge/src/cartridge/storage.rs

sbroad-cartridge/src/lib.rs

sbroad-core/src/executor/hash.rs