feat: generate metadata from the plan

sbroad-cartridge/src/api/exec_query.rs

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/groupby_test.lua

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

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

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

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

...rtridge/test_app/test/integration/target_queries_test.lua

sbroad-core/src/errors.rs

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