Add LAVAv2 job templates.

common-boot-tpl.yaml flashes the specified Apertis image to be tested.
Any tests to be run on have to be run in a separate namespace after a
reboot.

minimal-boot-tpl.yaml doesn't flash any images, but just boots into
a device-specific kernel and a minimal Debian stretch rootfs, listing
the available disks. This template is for testing basic hardware
functionality.

misc/lsdisk.yaml is a new test used by minimal-boot-tpl.yaml to list
the available disks.

Signed-off-by: Andrew Shadura <andrew.shadura@collabora.co.uk>
Reviewed-by: Luis Araujo <luis.araujo@collabora.co.uk>
Differential Revision: https://phabricator.apertis.org/D7208