Comment 7 for bug 1827929

We will need two formats for the hybrid mode, ptable: gpt and ptable: dos

For gpt, the config from comment #1 applies, we'll have both bios_grub and an efi partition (possibly a secondary for resilient boot).

For dos, we'll have:

    config:
      - id: main_disk
        type: disk
        ptable: dos
        serial: disk-a
        name: main_disk
        wipe: superblock
      - device: main_disk
        id: main_disk_part1
        number: 1
        size: 10G
        type: partition
        grub_device: true
        flag: boot
      - device: main_disk
        id: main_disk_part2
        number: 2
        size: 512M
        type: partition
        grub_device: true
        flag: esp
        wipe: superblock

Curtin currently uses 'boot' to mean toggle the DOS boot flag so we'll need to
do something to trigger marking this. I've suggested 'esp' here to
map to the 0xef code and we'll need to see if parted will let us do this, or
use sfdisk or something else to directly toggle the type.