[Libguestfs] [PATCH v2v v2 0/3] Use host-model

Version 1 was here: https://listman.redhat.com/archives/libguestfs/2023-February/thread.html#... I made a few changes in v2 but overall decided to keep the now unused gcaps_arch_min_version capability. This doesn't preclude removing it in future if we think it's never going to be useful. I changed patch 1 so that to remove the long comment about how the field is used, anticipating the later patches. I changed patch 2 as Laszlo suggested. I changed patch 3 as Laszlo suggested, but this also allows us to use Option.default so it becomes a nice one-liner. Rich.