rootfs-handoff: add UUID= and LABEL= support for root= parameter

rootfs-handoff: add UUID= and LABEL= support for root= parameter

- Added ext2_get_uuid_label() function in ext2.c to extract UUID and volume name
- Added format_uuid() helper to format 16-byte UUID to string format
- Added uuid_matches() helper to compare UUID string with binary UUID
- Added resolve_by_uuid_label() function in init.c to scan block devices and partitions
- Modified init_resolve_mount_device() to recognize UUID= and LABEL= prefixes
- Scans all ATA devices (hda-hdd) and their partitions (hda1-hda4)
- Supports ext2 filesystems (UUID and volume name from superblock)
- This implements the 'UUID= and LABEL= support' item from ROOTFS_HANDOFF_PLAN.md

Test Results:
- Smoke test: 131/131 PASS
- Battery test: 157/157 PASS
- Analyzer: PASS
- Zero regressions