improving RAIDframe

RAIDFrame is NetBSD’s kernel-level software RAID framework, providing RAID 0, 1, 4, 5, and 6 functionality. Its current implementation has limitations: n-way RAID 1 is limited, RAID 6 performance can be improved, and the system lacks robust scrubbing support to detect and correct silent data corruption. This project will implement n-way RAID 1, RAID scrubbing, and RAID 6 improvements to enhance reliability, performance, and maintainability.