Implement least_used load balancing algorithm for multi-disk configuration

Why it matters

This feature addresses the need to distribute data more evenly across multiple disks in a volume by selecting the disk with the least usage. It helps optimize disk utilization, improve performance, and prevent hotspots on specific disks.

How to use it

To enable this feature, configure your volume with the least_used load balancing algorithm in your ClickHouse configuration file when defining multi-disk volumes.