Replace LABELs with UUIDs

Currently archisodevice is got from /dev/disk/by-label/$archisolabel; this is not ok because if multiple ISOs built on different days in the same month are inserted into the computer, a seemingly random one is chosen.

This could be solved by selecting the partition by UUID instead of by LABEL.

This is already implemented in mkinitcpio/mkinitcpio-archiso!25.

This is an issue with the boot loader configuration files in archlinux/archiso> or mkarchiso relying on iso_label in profiledef.sh, not mkinitcpio-archiso.

assigned to @nl6720

mentioned in merge request !306 (merged)

changed milestone to %v70

closed with commit 3f95d391

mentioned in merge request !314 (merged)

mentioned in merge request !319 (merged)