add some alerts that are common when symbols is le struggle

Created by: DaedalusG

These are alerts that Dropbox has been seeing. After looking at some logs for the slow searches they were all symbols searches. I've requested that they add another big gitserver on top of the one powerful one they've provisioned. I'm a little uncertain about the symbols alert here, but I think this is all accurate. The customer isn't reporting that any of their grafana provisioning for any of these services looks like its hitting limits.