* Move rauc.db to boot partition
The RAUC metadata file contains information that is tightly related to the
system and kernel partitions. With the possibility to migrate data disk, the
rauc.db can contain bogus information when moved to a different system. Removal
of the file on "device wipe" is also not desirable, because the information
about slot status is lost.
Relocate the rauc.db to the boot partition after a system upgrade (as this
can't be handled by RAUC hooks, because it needs to be executed after all slots
and metadata is written) and adjust the script for recreating it. The downside
is that its content in /mnt/data would be recreated if the boot slot is changed
or system downgraded but this should be handled quite gracefully.
Also remove the raucdb-first-boot service which is no longer necessary
with the file not present in the data partition.
* Fix shellcheck and mount path
RAUC currently doesn't know the version of the booted slot when booted for the
first time or after wiping the data partition. As a result `ha os info` is
missing this information too.
As there's no built-in mechanism for generating these data by RAUC itself, add
a oneshot service that checks if the boot slot information is contained in the
rauc.db and if not, then generate it.
RAUC seems to cope quite well even with bogus data contained in rauc.db but in
any case, a test has been added to check that everything works as expected.
