Reduce number of calls to IsCRTEnabled (#23963)

In a single createPost flow, there were
3 separate calls to App.IsCRTEnabled. This
showed up very slightly in the CPU profiles.

Not a big deal, but good to get it out of
the way.

```release-note
NONE
```

server/channels/app/channel.go

@@ -2953,7 +2953,7 @@ func (a *App) SearchChannelsUserNotIn(c request.CTX, teamID string, userID strin
 	return channelList, nil
 }
 
-func (a *App) MarkChannelsAsViewed(c request.CTX, channelIDs []string, userID string, currentSessionId string, collapsedThreadsSupported bool) (map[string]int64, *model.AppError) {
+func (a *App) MarkChannelsAsViewed(c request.CTX, channelIDs []string, userID string, currentSessionId string, collapsedThreadsSupported, isCRTEnabled bool) (map[string]int64, *model.AppError) {
 	// I start looking for channels with notifications before I mark it as read, to clear the push notifications if needed
 	channelsToClearPushNotifications := []string{}
 	if a.canSendPushNotifications() {
@@ -2996,7 +2996,7 @@ func (a *App) MarkChannelsAsViewed(c request.CTX, channelIDs []string, userID st
 	}
 
 	var err error
-	updateThreads := *a.Config().ServiceSettings.ThreadAutoFollow && (!collapsedThreadsSupported || !a.IsCRTEnabledForUser(c, userID))
+	updateThreads := *a.Config().ServiceSettings.ThreadAutoFollow && (!collapsedThreadsSupported || !isCRTEnabled)
 	if updateThreads {
 		err = a.Srv().Store().Thread().MarkAllAsReadByChannels(userID, channelIDs)
 		if err != nil {
@@ -3026,7 +3026,7 @@ func (a *App) MarkChannelsAsViewed(c request.CTX, channelIDs []string, userID st
 		a.clearPushNotification(currentSessionId, userID, channelID, "")
 	}
 
-	if updateThreads && a.IsCRTEnabledForUser(c, userID) {
+	if updateThreads && isCRTEnabled {
 		timestamp := model.GetMillis()
 		for _, channelID := range channelIDs {
 			message := model.NewWebSocketEvent(model.WebsocketEventThreadReadChanged, "", channelID, userID, nil, "")
@@ -3057,7 +3057,7 @@ func (a *App) ViewChannel(c request.CTX, view *model.ChannelView, userID string,
 		return map[string]int64{}, nil
 	}
 
-	return a.MarkChannelsAsViewed(c, channelIDs, userID, currentSessionId, collapsedThreadsSupported)
+	return a.MarkChannelsAsViewed(c, channelIDs, userID, currentSessionId, collapsedThreadsSupported, a.IsCRTEnabledForUser(c, userID))
 }
 
 func (a *App) PermanentDeleteChannel(c request.CTX, channel *model.Channel) *model.AppError {