feat: add one subarena

sbroad-cartridge/src/cartridge/router.rs

sbroad-cartridge/src/cartridge/storage.rs

sbroad-core/src/backend/sql/ir.rs

sbroad-core/src/backend/sql/space.rs

sbroad-core/src/backend/sql/tree.rs

sbroad-core/src/executor.rs

sbroad-core/src/executor/bucket.rs

sbroad-core/src/executor/engine.rs

sbroad-core/src/executor/engine/helpers.rs

sbroad-core/src/executor/engine/helpers/storage.rs

sbroad-core/src/executor/engine/helpers/vshard.rs

sbroad-core/src/executor/engine/mock.rs

sbroad-core/src/executor/ir.rs

sbroad-core/src/executor/protocol.rs

sbroad-core/src/executor/result.rs

sbroad-core/src/executor/tests.rs

sbroad-core/src/executor/tests/exec_plan.rs

sbroad-core/src/executor/vtable.rs

sbroad-core/src/frontend/sql.rs

sbroad-core/src/frontend/sql/ir.rs