test/systemd.unit: Environment option object

Add an org.osbuild.systemd.unit stage using the new format for the
Environment option with two instances to the test manifest.

The contents of the new dropin file at
tree/usr/lib/systemd/system/boltd.service.d/30-boltd-debug.conf are:

[Service]
Environment="G_MESSAGES_DEBUG=all"
Environment="G_MESSAGES_TRACE=none"

test/data/stages/systemd.unit/b.json

@@ -636,6 +636,27 @@
               }
             }
           }
+        },
+        {
+          "type": "org.osbuild.systemd.unit",
+          "options": {
+            "unit": "boltd.service",
+            "dropin": "30-boltd-debug.conf",
+            "config": {
+              "Service": {
+                "Environment": [
+                  {
+                    "key": "G_MESSAGES_DEBUG",
+                    "value": "all"
+                  },
+                  {
+                    "key": "G_MESSAGES_TRACE",
+                    "value": "none"
+                  }
+                ]
+              }
+            }
+          }
         }
       ]
     }

test/data/stages/systemd.unit/b.mpp.yaml

@@ -45,3 +45,14 @@ pipelines:
           config:
             Unit:
               ConditionPathExists: /usr/lib/greenboot/greenboot
+      - type: org.osbuild.systemd.unit
+        options:
+          unit: boltd.service
+          dropin: 30-boltd-debug.conf
+          config:
+            Service:
+              Environment:
+                - key: "G_MESSAGES_DEBUG"
+                  value: "all"
+                - key: "G_MESSAGES_TRACE"
+                  value: "none"

test/data/stages/systemd.unit/diff.json

@@ -1,5 +1,7 @@
 {
   "added_files": [
+    "/usr/lib/systemd/system/boltd.service.d",
+    "/usr/lib/systemd/system/boltd.service.d/30-boltd-debug.conf",
     "/usr/lib/systemd/system/nm-cloud-setup.service.d",
     "/usr/lib/systemd/system/nm-cloud-setup.service.d/10-rh-enable-for-ec2.conf",
     "/usr/lib/systemd/user/grub-boot-success.timer.d",