feat: support left join with global tbl

sbroad-core/src/executor/ir.rs

sbroad-core/src/executor/vtable.rs

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

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

sbroad-core/src/ir/operator.rs

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

...ad-core/src/ir/transformation/redistribution/left_join.rs