Dashboard Controls: Fix schema transformation for link placement (#114630)

* fix: add missing transformation for scenes -> save model v2

* fix: link placement transformation on the backend between schemas

* fix: update the openapi spec in the tests

* tes: add tests for `transformSceneToSaveModelSchemaV2`

* tests: extend conversion_test.go to cover link placements

apps/dashboard/pkg/migration/conversion/testdata/input/v1beta1.dashboard-properties.json

@@ -70,6 +70,7 @@
         "title": "Documentation",
         "tooltip": "View documentation",
         "type": "link",
+        "placement": "inControlsMenu",
         "url": "https://docs.example.com/dashboard-guide"
       },
       {