Alerting: Fix route validation in provisioning service (#107550)

* introduce ExtraConfigsCrypto
* delete getLastConfiguration and move all code into method Get
* update legacy store to encrypt ExtraConfigs same way we do in MultiOrgAlertmanager
* update legacy store init
* delete PersistConfig
* remove unnecessary unmarshalling
* add better error

* add tests for legacy store

* add tests that cover extra config validation

* add integration test for conflicting routes

---------

Signed-off-by: Yuri Tseretyan <yuriy.tseretyan@grafana.com>

pkg/services/provisioning/provisioning.go

@@ -294,7 +294,7 @@ func (ps *ProvisioningServiceImpl) ProvisionAlerting(ctx context.Context) error
 		ps.alertingStore,
 		ps.alertingStore,
 		ps.folderService,
-		//ps.dashboardService,
+		// ps.dashboardService,
 		ps.quotaService,
 		ps.SQLStore,
 		int64(ps.Cfg.UnifiedAlerting.DefaultRuleEvaluationInterval.Seconds()),
@@ -304,7 +304,7 @@ func (ps *ProvisioningServiceImpl) ProvisionAlerting(ctx context.Context) error
 		notifier.NewCachedNotificationSettingsValidationService(ps.alertingStore),
 		alertingauthz.NewRuleService(ps.ac),
 	)
-	configStore := legacy_storage.NewAlertmanagerConfigStore(ps.alertingStore)
+	configStore := legacy_storage.NewAlertmanagerConfigStore(ps.alertingStore, notifier.NewExtraConfigsCrypto(ps.secretService))
 	receiverSvc := notifier.NewReceiverService(
 		alertingauthz.NewReceiverAccess[*ngmodels.Receiver](ps.ac, true),
 		configStore,