agetty from util-linux 2.35 (not yet packaged) supports reading issue files
from /run and /usr in the following way:

if /etc/issue exists:
   read /etc/issue and /etc/issue.d
else if /run/issue exists or /run/issue.d has any files
   read those
else
   read /usr/lib/issue
   read /usr/lib/issue.d

Moreover, the \4 and \6 escape codes use the first configured interface to
print the IP address.

That means for the most useful default case we don't need to run the extra code
of issue generator to enumerate network interfaces and merge issue files
anymore. We can rely on agetty built-in features only. Those who need the extra
features to print ssh keys or custom computed stuff could still install
issue-generator. So I propose the following change:

- don't hard require issue-generator in openSUSE-release
- don't ship /etc/issue
- ship /usr/lib/issue.d/10-openSUSE.issue with the following content:
  Welcome to \S{PRETTY_NAME} \S{VERSION_ID} - Kernel \r (\l).
  \4 \6