Add a new column parts_in_progress_names to system

Why it matters

This feature enhances diagnostics for mutations by showing the names of parts that are in progress during a mutation operation. It helps users understand the current state of mutations and troubleshoot or monitor mutation progress more effectively.

How to use it

Users can query the system.mutations system table and inspect the new parts_in_progress_names column to see which parts are currently being mutated. For example:

SELECT mutation_id, parts_in_progress_names FROM system.mutations
WHERE is_done = 0;