test/data: persist the journal for ostree images

Include the new journald config stage to configure journald to
persist the journal. This is needed since we don't create the
`/var/log/journal` directory that journald uses to switch the
default to persistent storage. But instead of creating that
directory, we explicitly configure journald via the new stage.
This is also what Fedora CoreOS does.

test/data/manifests/fedora-ostree-commit.json

@@ -901,6 +901,17 @@
             "language": "en_US.UTF-8"
           }
         },
+        {
+          "type": "org.osbuild.systemd-journald",
+          "options": {
+            "filename": "10-persistent.conf",
+            "config": {
+              "Journal": {
+                "Storage": "persistent"
+              }
+            }
+          }
+        },
         {
           "type": "org.osbuild.selinux",
           "options": {

test/data/manifests/fedora-ostree-commit.mpp.json

@@ -108,6 +108,17 @@
             "language": "en_US.UTF-8"
           }
         },
+        {
+          "type": "org.osbuild.systemd-journald",
+          "options": {
+            "filename": "10-persistent.conf",
+            "config": {
+              "Journal": {
+                "Storage": "persistent"
+              }
+            }
+          }
+        },
         {
           "type": "org.osbuild.selinux",
           "options": {

test/data/manifests/fedora-ostree-image.json

@@ -901,6 +901,17 @@
             "language": "en_US.UTF-8"
           }
         },
+        {
+          "type": "org.osbuild.systemd-journald",
+          "options": {
+            "filename": "10-persistent.conf",
+            "config": {
+              "Journal": {
+                "Storage": "persistent"
+              }
+            }
+          }
+        },
         {
           "type": "org.osbuild.selinux",
           "options": {