This patch deprecates the ifname field for specific metrics events of types DhcpClientEvent, DhcpErrorEvent, IpReachabilityEvent and IpManagerEvent. Instead ifnames are logged in ConnectivityMetricsEvent, allowing for link layer inference. Test: updated unit tests, $ runtest frameworks-net passes Bug: 34901696 Change-Id: I8bfabcb115bbd5289471d653c153a40bb48f28cd