Add a new MergeTree

Why it matters

This feature enables users to control and limit the number of dynamic subcolumns created in the Wide part of MergeTree tables after data merges. It solves the problem of unbounded growth in dynamic subcolumns which can negatively impact storage and performance by enforcing an upper limit independent of the data type settings.

How to use it

Set the merge_max_dynamic_subcolumns_in_wide_part setting in the MergeTree table settings configuration to specify the maximum allowed number of dynamic subcolumns in the Wide part after merging. This setting overrides the limits specified by the data types.