Replace sgdisk with sfdisk in kiwi and dracut GPT partition flows

[Copilot]

This updates GPT partition handling under kiwi/ and dracut/ to use sfdisk instead of sgdisk. The change covers partition creation, type updates, GPT/MBR transitions, and image/disk initialization paths that previously depended on sgdisk.

• GPT partitioner migration

  • Reworked kiwi/partitioner/gpt.py to drive GPT operations through sfdisk.
  • Switched partition creation to scripted sfdisk input, including explicit partition numbers, names, sizes, and optional start sectors.
  • Replaced GPT type updates with sfdisk --part-type.
  • Replaced GPT table resizing with sfdisk --dump + table-length: rewrite.

• Disk/table rewrite paths

  • Replaced GPT wipe/reinitialize logic in kiwi/storage/disk.py with sfdisk --wipe always and explicit label recreation.
  • Reworked GPT→MBR and hybrid GPT/MBR generation to emit sfdisk layouts instead of sgdisk transforms.

• Bootloader image creation

  • Updated the embedded EFI FAT image setup in kiwi/bootloader/config/systemd_boot.py to create its GPT partition via sfdisk.

• Dracut runtime changes

  • Replaced GPT partition delete/create/type operations in dracut/modules.d/59kiwi-lib/kiwi-partitions-lib.sh with sfdisk.
  • Reworked hybrid GPT creation in dracut to build the nested MBR with sfdisk --label-nested=mbr.
  • Dropped sgdisk from the dracut module runtime dependency list.

• Packaging/test alignment

  • Updated unit tests to assert the new sfdisk command shapes and scripted input flow.

Example of the new GPT partition creation pattern:

printf 'start=4096, size=100MiB, name="p.lxroot"\n' \
  | sfdisk --force -N 1 /dev/loop0

sfdisk --part-type /dev/loop0 1 0FC63DAF-8483-4772-8E79-3D69D8477DE4

[schaefi]

This change cannot be made because sfdisk does not support to create partition entries with custom partition IDs. For example see:

• https://download.opensuse.org/tumbleweed/repo/oss

 efipart_id="55"
 rootpart_id="1"
 bootpart_id="101"

Something like this cannot be represented by sfdisk as it creates new partitions with auto ID assignment according to their location in the table. That actually makes sense but we cannot afford to lose this feature in kiwi.

[github-actions]

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