Alerting: Use stable identifier of a group,contact point,mute timing when export to HCL (#90917)

---------

Signed-off-by: Aviv Guiser <avivguiser@gmail.com>

pkg/services/ngalert/api/util.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"hash/fnv"
 	"io"
 	"net/http"
 	"net/url"
@@ -230,3 +231,12 @@ func containsProvisionedAlerts(provenances map[string]ngmodels.Provenance, rules
 	}
 	return false
 }
+
+func getHash(hashSlice []string) uint64 {
+	sum := fnv.New64()
+	for _, str := range hashSlice {
+		_, _ = sum.Write([]byte(str))
+	}
+	hash := sum.Sum64()
+	return hash
+}