Alerting: Fix migration to not add label "alertname" (grafana#56509)

* do not add label alertname because it is overridden in state manager anyway
* update state manager to not consider labels with same value as dupe

(cherry picked from commit e2f1201)

# Conflicts:
#	pkg/services/ngalert/state/cache.go

pkg/services/ngalert/state/cache.go

@@ -44,16 +44,18 @@ func (c *cache) getOrCreate(ctx context.Context, alertRule *ngModels.AlertRule,
 		lbs[key] = val
 	}
 	for key, val := range ruleLabels {
-		_, ok := lbs[key]
+		ruleVal, ok := lbs[key]
 		// if duplicate labels exist, reserved label will take precedence
 		if ok {
-			dupes[key] = val
+			if ruleVal != val {
+				dupes[key] = val
+			}
 		} else {
 			lbs[key] = val
 		}
 	}
 	if len(dupes) > 0 {
-		c.log.Warn("rule declares one or many reserved labels. Those rules labels will be ignored", "labels", dupes)
+		c.log.Warn("Rule declares one or many reserved labels. Those rules labels will be ignored", "labels", dupes)
 	}
 	dupes = make(data.Labels)
 	for key, val := range result.Instance {

pkg/services/sqlstore/migrations/ualert/alert_rule.go

@@ -100,7 +100,6 @@ func addMigrationInfo(da *dashAlert) (map[string]string, map[string]string) {
 func (m *migration) makeAlertRule(cond condition, da dashAlert, folderUID string) (*alertRule, error) {
 	lbls, annotations := addMigrationInfo(&da)
 	name := normalizeRuleName(da.Name)
-	lbls["alertname"] = name
 	annotations["message"] = da.Message
 	var err error