[BP 7.2.6] - XDCR - log network latency as part of pre-check results

https://github.com/couchbase/goxdcr/blob/0aeaf8d41641e47c74cb5e92956404cfa0672d0c/peerToPeer/peerToPeerResults/connectionPreCheckStore.go#L21-L25

Currently pre-check only captures actual errors. Pre-check should be enhanced such that latency can be displayed as part of the result - and potentially look into a "high latency" threshold and display warning if the latency is too high.