Add setting for max file segment size in background download cache

Why it matters

This feature allows finer control over background download operations in the filesystem cache by limiting the size of file segments downloaded in the background. It helps optimize cache management and resource usage, improving system efficiency and performance when dealing with large files.

How to use it

To enable or configure this feature, set the background_download_max_file_segment_size parameter in your ClickHouse server configuration. Adjust the value to specify the maximum segment size (in bytes) for background file downloads within the filesystem cache.