Added system.merge_tree_settings table

Why it matters

This feature provides users with an easy way to view and inspect the current settings of MergeTree tables directly through a system table, enhancing transparency and ease of management for table-specific configurations.

How to use it

Users can query the system.merge_tree_settings table using standard SQL queries to retrieve the MergeTree settings. For example:

SELECT * FROM system.merge_tree_settings WHERE database = 'your_database' AND table = 'your_table'