Add production tools for secure boot SRK writing

• Fix Command set_lan_mac_otp: Fix miscalculation of second MAC address if MAC address starts with zero
• Add commands and infrastructure for handling SRK keys for secure boot: New commands activate_secure_boot, fuse_srk_keys, get_srk_keys, get_cpu_serial_no
• Command flash_emmc_wic: Add configuration option b_resize_emmc to suppress resizing ext4 partition on eMMC. Default is b_resize_emmc=1 for compatibility.
• Command flash_bl2emmc:
  • Add configuration value BOOTLOADER_OFFSET_KB. Default is 33 kBytes.
  • Set bootbus configuration for eMMC: mmc bootbus set single_backward x1 x8
• Add convenience command get_bootconfig