Added MergeTree Settings for Controlling TTL Merges with Compatibility Considerations

Added MergeTree settings (max_replicated_merges_with_ttl_in_queue and max_number_of_merges_with_ttl_in_pool) to control the number of merges with TTL in the background pool and replicated queue. This change breaks compatibility with older versions only if you use delete TTL. Otherwise, replication will stay compatible. You can avoid incompatibility issues if you update all shard replicas at once or execute SYSTEM STOP TTL MERGES until you finish the update of all replicas. If you'll get an incompatible entry in the replication queue, first of all, execute SYSTEM STOP TTL MERGES and after ALTER TABLE ... DETACH PARTITION ... the partition where incompatible TTL merge was assigned. Attach it back on a single replica. #14490 (alesapin).