fix: generate anonimous expression alias in lowercase

sbroad-cartridge/test_app/test/integration/api_test.lua

.../test_app/test/integration/arbitrary_expressions_test.lua

...d-cartridge/test_app/test/integration/arithmetic_test.lua

sbroad-cartridge/test_app/test/integration/cte_test.lua

sbroad-cartridge/test_app/test/integration/explain_test.lua

sbroad-cartridge/test_app/test/integration/groupby_test.lua

...tridge/test_app/test/integration/left_outer_join_test.lua

sbroad-cartridge/test_app/test/integration/limit_test.lua

...ad-cartridge/test_app/test/integration/operators_test.lua

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

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

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

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

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

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

sbroad-core/src/frontend/sql.rs

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

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

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

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