Teku 26.2.0 Update Brings Key Fixes and Performance Improvements

PegaSys recommended update fixes bugs and improves performance for Teku protocol developers. Upgrade to 26.2.0 defaulting RocksDB, not automatic migration from LevelDB. Ensure checkpoint-sync-url or initial-state is set before migrating to avoid startup failure. Other updates include data columns sidecar backfiller and new CLI flags, but require attention to high CPU usage and p2p peer upper bounds.