tests/ostree-rebase: split to uefi and bios

This test used to spawn two VMs at the same time which requires more
memory than the Openstack ci medium runner can provide. We want to be
using only medium runners so this change is necesasry to allow that.

.gitlab-ci.yml

@@ -378,12 +378,26 @@ OSTree raw image:
           - rhos-01/rhel-9.1-nightly-x86_64
           - rhos-01/centos-stream-9-x86_64
 
-Rebase OSTree:
+Rebase OSTree BIOS:
   stage: test
   extends: OSTree
   script:
     - schutzbot/deploy.sh
-    - /usr/libexec/tests/osbuild-composer/ostree-rebase.sh
+    - /usr/libexec/tests/osbuild-composer/ostree-rebase-bios.sh
+  parallel:
+    matrix:
+      - RUNNER:
+          - rhos-01/rhel-8.7-nightly-x86_64
+          - rhos-01/rhel-9.1-nightly-x86_64
+          - rhos-01/centos-stream-8-x86_64
+          - rhos-01/centos-stream-9-x86_64
+
+Rebase OSTree UEFI:
+  stage: test
+  extends: OSTree
+  script:
+    - schutzbot/deploy.sh
+    - /usr/libexec/tests/osbuild-composer/ostree-rebase-uefi.sh
   parallel:
     matrix:
       - RUNNER: