MM-21357: Use typed constants ClusterEvent (#17920)

* MM-21357: Use typed constants ClusterEvent

Use typed constants for:
- model.ClusterEvent

https://mattermost.atlassian.net/browse/MM-21357

```release-note
Use typed constant for model.ClusterEvent
```

* trigger CI
```release-note
NONE
```

services/cache/provider.go

@@ -5,6 +5,8 @@ package cache
 
 import (
 	"time"
+
+	"github.com/mattermost/mattermost-server/v5/model"
 )
 
 // CacheOptions contains options for initializaing a cache
@@ -12,7 +14,7 @@ type CacheOptions struct {
 	Size                   int
 	DefaultExpiry          time.Duration
 	Name                   string
-	InvalidateClusterEvent string
+	InvalidateClusterEvent model.ClusterEvent
 	Striped                bool
 	StripedBuckets         int
 }