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
```

model/role.go

@@ -554,7 +554,7 @@ func ChannelModeratedPermissionsChangedByPatch(role *Role, patch *RolePatch) []s
 }
 
 // GetChannelModeratedPermissions returns a map of channel moderated permissions that the role has access to
-func (r *Role) GetChannelModeratedPermissions(channelType string) map[string]bool {
+func (r *Role) GetChannelModeratedPermissions(channelType ChannelType) map[string]bool {
 	moderatedPermissions := make(map[string]bool)
 	for _, permission := range r.Permissions {
 		if _, found := ChannelModeratedPermissionsMap[permission]; !found {