Xen artifacts destined for `/boot` should get an `-edera` suffix to avoid host collisions with other Xen installs

e.g. our Xen today deploys as

• /boot/xen.gz

which can conflict with/be overwritten by other Xen installs from the host package manager or manual Xen installs, and should probably be:

• /boot/xen-edera.gz

etc.

See also: https://github.com/edera-dev/linux-kernel-oci/issues/122