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/store.go

@@ -220,7 +220,7 @@ type ChannelStore interface {
 	UpdateLastViewedAtPost(unreadPost *model.Post, userID string, mentionCount, mentionCountRoot int, updateThreads bool, setUnreadCountRoot bool) (*model.ChannelUnreadAt, error)
 	CountPostsAfter(channelID string, timestamp int64, userID string) (int, int, error)
 	IncrementMentionCount(channelID string, userID string, updateThreads, isRoot bool) error
-	AnalyticsTypeCount(teamID string, channelType string) (int64, error)
+	AnalyticsTypeCount(teamID string, channelType model.ChannelType) (int64, error)
 	GetMembersForUser(teamID string, userID string) (*model.ChannelMembers, error)
 	GetMembersForUserWithPagination(teamID, userID string, page, perPage int) (*model.ChannelMembers, error)
 	AutocompleteInTeam(teamID string, term string, includeDeleted bool) (*model.ChannelList, error)