New Setting to Optimize Memory Usage for Composite Primary Keys in ClickHouse

If the table's primary key contains mostly useless columns, don't keep them in memory. This is controlled by a new setting primary_key_ratio_of_unique_prefix_values_to_skip_suffix_columns with the value 0.9 by default, which means: for a composite primary key, if a column changes its value for at least 0.9 of all the times, the next columns after it will be not loaded. #60255 (Alexey Milovidov).