Add Subcolumn Sizes to system.parts_columns Table

Why it matters

This feature enhances observability by providing detailed size information of subcolumns within data parts. It allows users to better understand the storage distribution at a more granular level, aiding in optimization and troubleshooting.

How to use it

Users can query the system.parts_columns table as usual; the new columns representing subcolumn sizes will be available automatically without additional configuration.