ipn/{ipnstate,ipnlocal}: add integer NodeID to PeerStatus

In aa5da2e5f2 we made the IPN bus include deltas, including the
PeersRemoved, sending a slice of integer NodeIDs that were
removed. But when updating xcode, I realized there was no way to map
those integers to the stable node IDs used in other places.

I was consdering changing the just-added ipn.Notify.PeersRemoved from
an IntID to a string StableID, but then it doesn't match the MapResponse
wire protocol, which we've tried to match so far.

Instead, just add the integer ID as well. Callers can use whichever
world they want, having both. It's a little regrettable that we still
have two worlds of IDs, but oh well. Neither is really suitable to a
hypothetical future fully federated world of control servers anyway,
so we'll need a third type later anyway, so just live with the two we
have for now.

Updates #12542

Change-Id: Ib8fd48a265e1da1f8779152f141f624a7f7260e9
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

ipn/ipnlocal/local.go

@@ -1516,6 +1516,7 @@ func (b *LocalBackend) populatePeerStatusLocked(sb *ipnstate.StatusBuilder) {
 func peerStatusFromNode(ps *ipnstate.PeerStatus, n tailcfg.NodeView) {
 	ps.PublicKey = n.Key()
 	ps.ID = n.StableID()
+	ps.NodeID = n.ID()
 	ps.Created = n.Created()
 	ps.ExitNodeOption = buildfeatures.HasUseExitNode && tsaddr.ContainsExitRoutes(n.AllowedIPs())
 	if n.Tags().Len() != 0 {

ipn/ipnstate/ipnstate.go

@@ -223,6 +223,7 @@ type PeerStatusLite struct {
 // inconsistencies or lost data in the peer status.
 type PeerStatus struct {
 	ID        tailcfg.StableNodeID
+	NodeID    tailcfg.NodeID
 	PublicKey key.NodePublic
 	HostName  string // HostInfo's Hostname (not a DNS name or necessarily unique)
 
@@ -443,6 +444,9 @@ func (sb *StatusBuilder) AddPeer(peer key.NodePublic, st *PeerStatus) {
 	if v := st.ID; v != "" {
 		e.ID = v
 	}
+	if v := st.NodeID; v != 0 {
+		e.NodeID = v
+	}
 	if v := st.HostName; v != "" {
 		e.HostName = v
 	}