fix: refactoring after rebase on new protocol, tiers and subarenas

sbroad-cartridge/src/cartridge/router.rs

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

...test_app/test/integration/subquery_as_expression_test.lua

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

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

sbroad-core/src/executor/engine.rs

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

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

sbroad-core/src/executor/ir.rs

sbroad-core/src/executor/result.rs

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

sbroad-core/src/executor/tests.rs

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

sbroad-core/src/executor/vtable.rs

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

sbroad-core/src/frontend/sql.rs

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

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

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

sbroad-core/src/ir.rs