MM-15198 Migrate Channel.Get/GetFromMaster to Sync by default (#10667)

* MM-15198 Migrate Channel.Get/GetFromMaster to Sync by default

* MM-15198 - Update store/storetest/post_store.go

fix error handling in post_store.go test case

Co-Authored-By: andresoro <ao15@my.fsu.edu>

app/email_batching.go

@@ -216,12 +216,11 @@ func (s *Server) sendBatchedEmailNotification(userId string, notifications []*ba
 			continue
 		}
 
-		result := <-s.Store.Channel().Get(notification.post.ChannelId, true)
-		if result.Err != nil {
+		channel, errCh := s.Store.Channel().Get(notification.post.ChannelId, true)
+		if errCh != nil {
 			mlog.Warn("Unable to find channel of post for batched email notification")
 			continue
 		}
-		channel := result.Data.(*model.Channel)
 
 		emailNotificationContentsType := model.EMAIL_NOTIFICATION_CONTENTS_FULL
 		if license := s.License(); license != nil && *license.Features.EmailNotificationContents {