sys-apps/ignition: Use new upstream patch

[pothos]

The patch was reworked to use partx which already is in the initrd and to have safety checks for disks in use.

How to use

Wait for the upstream PR to be merged. Then resync and drop partprobe from bootengine (flatcar/bootengine#80) and update the commit here to the git merge commit ref.

Testing done

Tested three cases, the overwriting of USR-A was detected and an error thrown, the other two changes passed without problem because the USR-B is unused and can be overwritten and the new partition is also ok to add (confirmed with lsblk that the kernel has the updated values thanks to partx):

variant: flatcar
version: 1.0.0
storage:
  disks:
  - device: /dev/vda
    partitions:
    - label: USR-A
      number: 3
      size_mib: 1
      resize: true

variant: flatcar
version: 1.0.0
storage:
  disks:
  - device: /dev/vda
    partitions:
    - label: USR-B
      number: 4
      size_mib: 1
      resize: true

variant: flatcar
version: 1.0.0
storage:
  disks:
  - device: /dev/vda
    partitions:
    - label: VAR
      number: 10
      size_mib: 1
  filesystems:
  - device: /dev/disk/by-partlabel/VAR
    format: vfat
    path: /var
    label: VAR
    with_mount_unit: true

• Changelog entries added in the respective changelog/ directory (user-facing change, bug fix, security fix, update)
• Inspected CI output for image differences: /boot and /usr size, packages, list files for any missing binaries, kernel modules, config files, kernel modules, etc.

[github-actions]

Build action triggered: https://github.com/flatcar/scripts/actions/runs/10791826588

[tormath1]

This has been merged upstream and it will be pulled in the next Ignition upgrade. Thanks!