Generate new fixtures with cosa buildextend-live --fixture.  Run it, rename
the ISO, compress with `xz -9`, and check the compressed size.  If the size
is unreasonable, buildextend-live may need to be fixed.

embed-areas-2020-09.iso.xz
    coreiso+ header pointing to ignition.img embed area

embed-areas-2021-01.iso.xz
    coreiso+ header pointing to ignition.img embed area
    coreKarg header pointing to kargs areas and defaults in /.cmdline

embed-areas-2021-09.iso.xz
    coreiso+ header pointing to ignition.img embed area
    coreKarg header pointing to kargs areas and defaults in /.cmdline
    kargs.json pointing to kargs areas and embedding defaults

embed-areas-2021-12.iso.xz
    coreiso+ header pointing to ignition.img embed area
    coreKarg header pointing to kargs areas and defaults in /.cmdline
    kargs.json pointing to kargs areas and embedding defaults
    miniso.dat version 1
    features.json: installer-config, live-initrd-network

embed-areas-2022-02.iso.xz
    kargs.json pointing to kargs areas and embedding defaults
    miniso.dat version 1
    features.json: installer-config, live-initrd-network

embed-areas-2022-09.iso.xz
    kargs.json pointing to kargs areas and embedding defaults
    miniso.dat version 1
    features.json: installer-config, installer-config-directives,
        live-initrd-network
    installer-config-directives from 0.16.0

embed-areas-2023-03.x86_64.iso.xz
    igninfo.json pointing to ignition.img (no offset and no length)
    kargs.json pointing to kargs areas and embedding defaults
    miniso.dat version 1
    features.json: installer-config, installer-config-directives,
        live-initrd-network
    installer-config-directives from 0.16.0

embed-areas-2023-03.s390x.iso.xz
    igninfo.json pointing to cdboot.img (offset and length)
    no kargs.json
    miniso.dat version 1
    features.json: installer-config, installer-config-directives,
        live-initrd-network
    installer-config-directives from 0.16.0
