[v9.4.x] Alerting: Pause dash alerts on migration (#62830)

Alerting: Pause dash alerts on migration (#62798)

* Alerting: Pause dash alerts on migration

(cherry picked from commit f49efa6e27)

Co-authored-by: George Robinson <george.robinson@grafana.com>

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

@@ -5,6 +5,7 @@ import (
 
 	"github.com/grafana/grafana/pkg/infra/log"
 	"github.com/grafana/grafana/pkg/services/sqlstore/migrator"
+	"github.com/prometheus/alertmanager/silence/silencepb"
 )
 
 // newTestMigration generates an empty migration to use in tests.
@@ -19,5 +20,6 @@ func newTestMigration(t *testing.T) *migration {
 		seenUIDs: uidSet{
 			set: make(map[string]struct{}),
 		},
+		silences: make(map[int64][]*silencepb.MeshSilence),
 	}
 }