Alerting: Add Triage feature toggle (#110326)

* Add state history config to frontend config object

* Add alertingTriage feature toggle

* Add Triage menu entry

* Add old state history config props for backward compatibility

packages/grafana-runtime/src/config.ts

@@ -186,10 +186,18 @@ export class GrafanaBootConfig {
   unifiedAlertingEnabled = false;
   unifiedAlerting: UnifiedAlertingConfig = {
     minInterval: '',
-    alertStateHistoryBackend: undefined,
-    alertStateHistoryPrimary: undefined,
+    stateHistory: {
+      backend: undefined,
+      primary: undefined,
+      prometheusTargetDatasourceUID: undefined,
+      prometheusMetricName: undefined,
+    },
     recordingRulesEnabled: false,
     defaultRecordingRulesTargetDatasourceUID: undefined,
+
+    // Backward compatibility fields - populated by backend
+    alertStateHistoryBackend: undefined,
+    alertStateHistoryPrimary: undefined,
   };
   applicationInsightsConnectionString?: string;
   applicationInsightsEndpointUrl?: string;