QEMU images should have flatcar.autologin set as kernel parameter

[pothos]

Current situation

The graphical/serial console for QEMU images requires the user to log in with a password. Normally, no passwords are set because SSH keys are used for login.
To use the graphical/serial console the user needs to reboot the machine and manually append flatcar.autologin to the kernel command line parameters in GRUB.

Impact
A reboot is needed (assumed people actually know about that kernel parameter!) or a password needs to be configured via Ignition.

Ideal future situation
flatcar.autologin is always part of the kernel command line for QEMU images. This is no security problem because a user with console access can add it in GRUB if wanted when the machine reboots.

Implementation options
A OEM package is created for QEMU, so that image_to_vm.sh --format=qemu (or =qemu_uefi or =qemu_uefi_secure) creates an OEM partition with the following contents.

grub.cfg:

set oem_id="qemu"
set linux_append="flatcar.autologin"

oem-release:

ID=qemu
VERSION_ID=x.y.z
NAME="qemu"
HOME_URL="https://www.qemu.org/"
BUG_REPORT_URL="https://issues.flatcar-linux.org"

(Where x.y.z is the built Flatcar CL version.)

Additional information

flatcar.autologin is also the default for the out-of-band console on, e.g., Packet.