refactor!: replace Buckets::Single with Any

sbroad-cartridge/src/cartridge/router.rs

sbroad-cartridge/src/cartridge/storage.rs

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

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

sbroad-core/src/executor/bucket.rs

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

sbroad-core/src/executor/engine.rs

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

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

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

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

sbroad-core/src/executor/vtable.rs

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

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

sbroad-core/src/ir/distribution.rs

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