fix core module for tests

sbroad-core/benches/engine.rs

sbroad-core/benches/parse.rs

sbroad-core/src/backend.rs

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

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

sbroad-core/src/executor.rs

sbroad-core/src/executor/engine.rs

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

sbroad-core/src/executor/hash.rs

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

sbroad-core/src/executor/ir.rs

sbroad-core/src/executor/tests.rs

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

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

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

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

sbroad-core/src/ir/transformation/bool_in/tests.rs

sbroad-core/src/ir/transformation/dnf/tests.rs

...-core/src/ir/transformation/equality_propagation/tests.rs

sbroad-core/src/ir/transformation/helpers.rs