refactoring: tests using sql transformations

src/frontend/sql/ir/tests.rs

src/ir/transformation.rs

src/ir/transformation/bool_in/tests.rs

src/ir/transformation/dnf/tests.rs

src/ir/transformation/equality_propagation/tests.rs

src/ir/transformation/helpers.rs

src/ir/transformation/merge_tuples/tests.rs

src/ir/transformation/redistribution/tests.rs

src/ir/transformation/split_columns/tests.rs