fix: special handling of unmarshalling for invalid json dashboards (#108519)

* implement special dashboard fallback logic when dashboard data has invalid json behind feature flag

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Co-authored-by: Will Assis <william@williamassis.com>

pkg/registry/apis/dashboard/legacy/testdata/postgres--query_dashboards-dashboard.sql

@@ -2,6 +2,7 @@ SELECT
   dashboard.org_id,
   dashboard.id,
   dashboard.uid,
+  dashboard.title,
   dashboard.folder_uid,
   dashboard.deleted,
   plugin_id,