kdumpctl: Add basic UKI support
    
    A Unified Kernel Image (UKI) is a single EFI PE executable combining an
    EFI stub, a kernel image, an initrd image, and the kernel command line.
    They are defined in the Boot Loader Specification [1] as type #2
    entries. UKIs have the advantage that all code as well as meta data that
    is required to boot the system, not only the kernel image, is combined
    in a single PE file and can be signed for EFI SecureBoot. This extends
    the coverage of SecureBoot extensively.
    
    For RHEL support for UKI were included into kernel-ark with 16c7e3ee836e
    ("redhat: Add sub-RPM with a EFI unified kernel image for virtual
    machines").
    
    There are two problems with UKIs from the kdump point of view at the
    moment. First, they cannot be directly loaded via kexec_file_load and
    second, the initrd included isn't suitable for kdump. In order to enable
    kdump on systems with UKIs build the kdump initrd as usual and extract
    the kernel image before loading the crash kernel.
    
    [1] https://uapi-group.org/specifications/specs/boot_loader_specification/
    
    Signed-off-by: Philipp Rudo <prudo@redhat.com>
    Reviewed-by: Pingfan Liu <piliu@redhat.com>
    Reviewed-by: Coiby Xu <coxu@redhat.com>