ClickHouse Keeper Now Uses ZSTD for Snapshots by Default

This is relevant only if you already started using the experimental clickhouse-keeper support. Now ClickHouse Keeper snapshots compressed with ZSTD codec by default instead of custom ClickHouse LZ4 block compression. This behavior can be turned off with compress_snapshots_with_zstd_format coordination setting (must be equal on all quorum replicas). Backward incompatibility is quite rare and may happen only when new node will send snapshot (happens in case of recovery) to the old node which is unable to read snapshots in ZSTD format. #29417 (alesapin).