feat: support LIMIT clause

doc/sql/query.ebnf

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

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

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

sbroad-core/src/executor/bucket.rs

sbroad-core/src/executor/ir.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/cte.rs

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

sbroad-core/src/frontend/sql/query.pest

sbroad-core/src/ir/explain.rs

sbroad-core/src/ir/helpers.rs

sbroad-core/src/ir/operator.rs

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

sbroad-core/src/ir/tree/relation.rs

sbroad-core/src/ir/tree/subtree.rs