cloud-localds: please switch from genisoimage to xorriso

Forwarded from https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1113907

cloud-image-utils depends on genisoimage, a cdrecord/mkisofs-like program. genisoimage (from wodim) is effectively unmaintained since years. Please switch to xorriso, which has a cdrecord/mkisofs compatibility mode.

It'd be good to get rid of genisoimage for forky. (Debian 14)