MM-23596: Ability to list private channels for team (#14925)

Summary:
store, app, api and go driver support for listing private channels

Ticket Link:
https://mattermost.atlassian.net/browse/MM-23596

store/timer_layer.go

@@ -1176,6 +1176,22 @@ func (s *TimerLayerChannelStore) GetPinnedPosts(channelId string) (*model.PostLi
 	return resultVar0, resultVar1
 }
 
+func (s *TimerLayerChannelStore) GetPrivateChannelsForTeam(teamId string, offset int, limit int) (*model.ChannelList, *model.AppError) {
+	start := timemodule.Now()
+
+	resultVar0, resultVar1 := s.ChannelStore.GetPrivateChannelsForTeam(teamId, offset, limit)
+
+	elapsed := float64(timemodule.Since(start)) / float64(timemodule.Second)
+	if s.Root.Metrics != nil {
+		success := "false"
+		if resultVar1 == nil {
+			success = "true"
+		}
+		s.Root.Metrics.ObserveStoreMethodDuration("ChannelStore.GetPrivateChannelsForTeam", success, elapsed)
+	}
+	return resultVar0, resultVar1
+}
+
 func (s *TimerLayerChannelStore) GetPublicChannelsByIdsForTeam(teamId string, channelIds []string) (*model.ChannelList, *model.AppError) {
 	start := timemodule.Now()