Fix Group By Issue in Distributed Queries with Mixed Version Shards

Fix incorrect GROUP BY (multiple rows with the same keys in result) in case of distributed query when shards had mixed versions <= 21.3 and >= 21.4, GROUP BY key had several columns all with fixed size, and two-level aggregation was activated (see group_by_two_level_threshold and group_by_two_level_threshold_bytes). Fixes #29580. #29735 (Nikolai Kochetov).