Add finished_download_time column to system

Why it matters

This feature improves debugging and monitoring by providing more informative error messages related to incomplete read ranges in filesystem cache operations. The addition of the finished_download_time column allows users to track when a file was fully downloaded into the cache, aiding in performance analysis and cache management.

How to use it

The improved exception messages are available automatically during runtime when the specific error occurs. Users can query the system.filesystem_cache table to check the finished_download_time column to monitor the completion timestamp of cached files without any extra configuration.