control/controlclient: introduce eventbus messages instead of callbacks (#16956)

This is a small introduction of the eventbus into controlclient that
communicates with mainly ipnlocal. While ipnlocal is a complicated part
of the codebase, the subscribers here are from the perspective of
ipnlocal already called async.

Updates #15160

Signed-off-by: Claus Lensbøl <claus@tailscale.com>

control/controlclient/controlclient_test.go

@@ -35,6 +35,7 @@ import (
 	"tailscale.com/types/logger"
 	"tailscale.com/types/netmap"
 	"tailscale.com/types/persist"
+	"tailscale.com/util/eventbus/eventbustest"
 )
 
 func fieldsOf(t reflect.Type) (fields []string) {
@@ -218,6 +219,8 @@ func TestDirectProxyManual(t *testing.T) {
 		t.Skip("skipping without --live-network-test")
 	}
 
+	bus := eventbustest.NewBus(t)
+
 	dialer := &tsdial.Dialer{}
 	dialer.SetNetMon(netmon.NewStatic())
 
@@ -239,6 +242,7 @@ func TestDirectProxyManual(t *testing.T) {
 		},
 		Dialer:       dialer,
 		ControlKnobs: &controlknobs.Knobs{},
+		Bus:          bus,
 	}
 	d, err := NewDirect(opts)
 	if err != nil {
@@ -263,6 +267,8 @@ func TestHTTPSWithProxy(t *testing.T) { testHTTPS(t, true) }
 func testHTTPS(t *testing.T, withProxy bool) {
 	bakedroots.ResetForTest(t, tlstest.TestRootCA())
 
+	bus := eventbustest.NewBus(t)
+
 	controlLn, err := tls.Listen("tcp", "127.0.0.1:0", tlstest.ControlPlane.ServerTLSConfig())
 	if err != nil {
 		t.Fatal(err)
@@ -327,6 +333,7 @@ func testHTTPS(t *testing.T, withProxy bool) {
 			t.Logf("PopBrowserURL: %q", url)
 		},
 		Dialer: dialer,
+		Bus:    bus,
 	}
 	d, err := NewDirect(opts)
 	if err != nil {