Increase max_replicated_merges_in_queue default from 16 to 1000 in ReplicatedMergeTree tables

Increase the default value of max_replicated_merges_in_queue for ReplicatedMergeTree tables from 16 to 1000. It allows faster background merge operation on clusters with a very large number of replicas, such as clusters with shared storage in ClickHouse Cloud. #47050 (Alexey Milovidov).