all: migrate code off Notify.NetMap to Notify.SelfChange

Move tailscaled's in-tree reactive users from of IPN bus Notify.NetMap
updates to the narrower Notify.SelfChange signal introduced earlier in
this series. Consumers that need additional state (peers, DNS config,
etc.) fetch it on demand via the LocalAPI.

It is a step toward the larger goal of not fanning Notify.NetMap out
to every bus watcher on Linux/non-GUI hosts.

A future change stops sending Notify.NetMap entirely on Linux and
non-GUI platforms. (eventually once macOS/iOS/Windows migrate to the
upcoming new Notify APIs, we'll remove ipn.Notify.NetMap entirely)

Updates #12542

Change-Id: I51ea9d86bdca1909d6ac0e7d5bd3934a3a4e8516
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/tailscale/cli/up.go

@@ -732,7 +732,7 @@ func runUp(ctx context.Context, cmd string, args []string, upArgs upArgsT) (retE
 			if s := n.State; s != nil {
 				ipnIsRunning = *s == ipn.Running
 			}
-			if n.NetMap != nil && n.NetMap.NodeKey != origNodeKey {
+			if n.SelfChange != nil && n.SelfChange.Key != origNodeKey {
 				waitingForKeyChange = false
 			}
 			if ipnIsRunning && !waitingForKeyChange {