MM-21357: Use typed constant for channel types (#17928)

* MM-21357: Use typed constant for channel types

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

```release-note
- Introduced a new type ChannelType for all channel types.
- Updated the Client4.UpdateChannelPrivacy method to ChannelType.
```

* Address review comments

```release-note
NONE
```

* telemetry fix

```release-note
NONE
```

store/retrylayer/retrylayer.go

@@ -588,7 +588,7 @@ func (s *RetryLayerChannelStore) AnalyticsDeletedTypeCount(teamID string, channe
 
 }
 
-func (s *RetryLayerChannelStore) AnalyticsTypeCount(teamID string, channelType string) (int64, error) {
+func (s *RetryLayerChannelStore) AnalyticsTypeCount(teamID string, channelType model.ChannelType) (int64, error) {
 
 	tries := 0
 	for {