v.20.8Bug Fix

Fixed max_replicated_logs_to_keep default value and improved lost replica recovery process

Fixed too low default value of max_replicated_logs_to_keep setting, which might cause replicas to become lost too often. Improve lost replica recovery process by choosing the most up-to-date replica to clone. Also do not remove old parts from lost replica, detach them instead. #15701 (tavplubix).