Alerting: Time interval Delete API to check for usages in alert rules (#90500)

* Check if a time interval is used in alert rules before deleting it
* Add time interval to parameters of ListAlertRulesQuery and ListNotificationSettings of DbStore

== Refacorings == 
* refactor isMuteTimeInUse to accept a single route
* update getMuteTiming to not return err
* update delete to get the mute timing from config first

pkg/tests/api/alerting/testing.go

@@ -240,6 +240,17 @@ type apiClient struct {
 	url string
 }
 
+type LegacyApiClient struct {
+	apiClient
+}
+
+func NewAlertingLegacyAPIClient(host, user, pass string) LegacyApiClient {
+	cli := newAlertingApiClient(host, user, pass)
+	return LegacyApiClient{
+		apiClient: cli,
+	}
+}
+
 func newAlertingApiClient(host, user, pass string) apiClient {
 	if len(user) == 0 && len(pass) == 0 {
 		return apiClient{url: fmt.Sprintf("http://%s", host)}