Add modification_time column to system.parts_columns

Why it matters

This feature introduces the modification_time column to track the last modification timestamp of parts columns metadata. It provides users with better visibility into when individual columns in table parts were last changed, aiding in debugging, auditing, and monitoring.

How to use it

Users can query the updated system.parts_columns table to see the modification_time value for each column in table parts, for example:

SELECT database, table, column, modification_time FROM system.parts_columns WHERE table = 'your_table_name'