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/timerlayer/timerlayer.go

@@ -534,7 +534,7 @@ func (s *TimerLayerChannelStore) AnalyticsDeletedTypeCount(teamID string, channe
 	return result, err
 }
 
-func (s *TimerLayerChannelStore) AnalyticsTypeCount(teamID string, channelType string) (int64, error) {
+func (s *TimerLayerChannelStore) AnalyticsTypeCount(teamID string, channelType model.ChannelType) (int64, error) {
 	start := timemodule.Now()
 
 	result, err := s.ChannelStore.AnalyticsTypeCount(teamID, channelType)