After an unattended install the harness now copies the installer's
timing file and log off the installed system, with systemd-analyze from
its first boot, next to the base image, so CI can report them without
attaching the disk. OMARCHY_INTEGRATION_DISK_CACHE sets the target
disk's QEMU cache mode; cache=none keeps the host page cache out of the
guest's writes, so install times measure the installer rather than the
host.