feat: namespace plugin permissions and keep them valid when a plugin is off

scripts/__fixtures__/manifests/valid-actions.json

@@ -14,10 +14,13 @@
   },
   "capabilities": ["kv:own", "ui:surface"],
   "contributes": {
-    "permissionGroup": {
-      "group": "sample-plugin",
-      "permissions": ["sample-plugin.use"]
-    },
+    "permissions": [
+      {
+        "name": "use",
+        "titleKey": "permissions.use.title",
+        "descriptionKey": "permissions.use.description"
+      }
+    ],
     "actions": [
       {
         "id": "sample.open",