ipn/ipnlocal,wgengine{/magicsock}: replace SetNetworkMap with eventbus (#16299)

Same with UpdateNetmapDelta.

Updates tailscale/corp#27502
Updates #15160

Signed-off-by: Jordan Whited <jordan@tailscale.com>

ipn/ipnlocal/local.go

@@ -1946,10 +1946,6 @@ var _ controlclient.NetmapDeltaUpdater = (*LocalBackend)(nil)
 
 // UpdateNetmapDelta implements controlclient.NetmapDeltaUpdater.
 func (b *LocalBackend) UpdateNetmapDelta(muts []netmap.NodeMutation) (handled bool) {
-	if !b.MagicConn().UpdateNetmapDelta(muts) {
-		return false
-	}
-
 	var notify *ipn.Notify // non-nil if we need to send a Notify
 	defer func() {
 		if notify != nil {