feature: Support ubuntu via storage.rawCosi option

[fintelia]

This adds a storage.rawCosi option which makes trident directly copy the COSI partitions (including ESP) onto the target disk and skips steps that would mess too much with the written image.

Example HC:

image:
  url: http://NETLAUNCH_HOST_ADDRESS/files/ubuntu.cosi
  sha384: ignored
trident:
  disable: true
storage:
  rawCosi: true
  disks:
    - id: os
      device: /dev/sda
      partitionTableType: gpt
      partitions:
        - id: esp
          size: 128M
          type: esp
        - id: boot
          size: 512M
        - id: root
          size: 48G
          type: root
  filesystems:
    - deviceId: esp
      mountPoint:
        path: /boot/efi
        options: umask=0077
    - deviceId: boot
      mountPoint: /boot
    - deviceId: root
      mountPoint: /
os:
  selinux:
    mode: disabled
scripts:
  postConfigure:
    - content: |
        sed -i "s/PARTUUID=[a-f0-9-]*/LABEL=cloudimg-rootfs/g" /etc/fstab
        sed -i "s/PARTUUID=[a-f0-9-]*/LABEL=cloudimg-rootfs/g" /boot/grub/grub.cfg
        sed -i "s/initrdfail=2/initrdfail=1/g" /boot/grub/grub.cfg
        sed -i '1s/^/set initrdfail=1\n/' /boot/grub/grub.cfg
      name: root-uuid
      runOn: [clean-install]

[jiria]

FWIW, the servicing env is azl3.

[fintelia]

The *-unknown-linux-musl part makes it produce a statically linked binary that can run on any Linux distribution without having to worry about glibc version conflicts