feat: support DISTINCT in projection

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

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

sbroad-core/src/frontend/sql.rs

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

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

sbroad-core/src/ir.rs

sbroad-core/src/ir/distribution/tests.rs

sbroad-core/src/ir/expression/tests.rs

sbroad-core/src/ir/operator.rs

sbroad-core/src/ir/operator/tests.rs

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

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

...ore/src/ir/transformation/redistribution/tests/segment.rs

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

...tifactory/backend/sql/tree/arbitrary_projection_plan.yaml

...ifactory/backend/sql/tree/arithmetic_projection_plan.yaml

...tifactory/backend/sql/tree/arithmetic_selection_plan.yaml

...sts/artifactory/backend/sql/tree/sql_order_selection.yaml

.../tests/artifactory/ir/distribution/shrink_dist_key_1.yaml

.../tests/artifactory/ir/distribution/shrink_dist_key_2.yaml