Add bootc to eln

To do this though add a `distro` variable we can use to differentiate
between stream9 vs not-stream9 for now.

bootc exists now in eln since
- https://pagure.io/pungi-fedora/pull-request/1217
- https://github.com/minimization/content-resolver-input/pull/1006

tier-0/manifest.yaml

@@ -49,8 +49,12 @@ remove-from-packages:
   # https://bugzilla.redhat.com/show_bug.cgi?id=2105177
   - [dbus-common, /usr/lib/sysusers.d/dbus.conf]
 
+conditional-include:
+  - if: distro != "stream9"
+    include: bootc.yaml
+
 include:
-  - bootc.yaml
+  - ostree.yaml
   - initramfs.yaml
 
 packages: