Adds the rocky-container-generic element

This makes the rocky-container build more like the generic cloud
image, see:

https://git.rockylinux.org/rocky/kickstarts/-/blob/r8/Rocky-8-GenericCloud.ks

Author: jovial

elements/rocky-container-generic/element-deps

@@ -0,0 +1,3 @@
+rocky-container
+package-installs
+cloud-init-datasources

elements/rocky-container-generic/package-installs.yaml

@@ -0,0 +1,22 @@
+chrony:
+dnf:
+yum:
+cloud-init:
+cloud-utils-growpart:
+NetworkManager:
+dracut-config-generic:
+dracut-norescue:
+firewalld:
+gdisk:
+grub2:
+kernel:
+nfs-utils:
+rsync:
+tar:
+dnf-utils:
+yum-utils:
+python3-jsonschema:
+qemu-guest-agent:
+dhcp-client:
+rocky-release:
+rng-tools:

elements/rocky-container-generic/post-install.d/50-cloud-init.sh

@@ -0,0 +1,8 @@
+if [ ${DIB_DEBUG_TRACE:-0} -gt 0 ]; then
+    set -x
+fi
+set -eu
+set -o pipefail
+
+echo -e 'rocky\tALL=(ALL)\tNOPASSWD: ALL' >> /etc/sudoers
+sed -i 's/name: cloud-user/name: rocky/g' /etc/cloud/cloud.cfg

elements/rocky-container-generic/pre-install.d/03-reinstall-core.sh

@@ -0,0 +1,9 @@
+if [ ${DIB_DEBUG_TRACE:-0} -gt 0 ]; then
+    set -x
+fi
+set -eu
+set -o pipefail
+
+# RUN this after DIB_DISTRIBUTION_MIRROR has been set up. It installs a
+# load of missing packages from the container image
+dnf install -y @core --allowerasing