ipn/ipnlocal,wgengine/magicsock: use eventbus for node & filter updates (#16271)

nodeBackend now publishes filter and node changes to eventbus topics
that are consumed by magicsock.Conn

Updates tailscale/corp#27502
Updates tailscale/corp#29543

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

ipn/ipnlocal/node_backend_test.go

@@ -8,10 +8,12 @@ import (
 	"errors"
 	"testing"
 	"time"
+
+	"tailscale.com/util/eventbus"
 )
 
 func TestNodeBackendReadiness(t *testing.T) {
-	nb := newNodeBackend(t.Context())
+	nb := newNodeBackend(t.Context(), eventbus.New())
 
 	// The node backend is not ready until [nodeBackend.ready] is called,
 	// and [nodeBackend.Wait] should fail with [context.DeadlineExceeded].
@@ -42,7 +44,7 @@ func TestNodeBackendReadiness(t *testing.T) {
 }
 
 func TestNodeBackendShutdown(t *testing.T) {
-	nb := newNodeBackend(t.Context())
+	nb := newNodeBackend(t.Context(), eventbus.New())
 
 	shutdownCause := errors.New("test shutdown")
 
@@ -80,7 +82,7 @@ func TestNodeBackendShutdown(t *testing.T) {
 }
 
 func TestNodeBackendReadyAfterShutdown(t *testing.T) {
-	nb := newNodeBackend(t.Context())
+	nb := newNodeBackend(t.Context(), eventbus.New())
 
 	shutdownCause := errors.New("test shutdown")
 	nb.shutdown(shutdownCause)
@@ -92,7 +94,7 @@ func TestNodeBackendReadyAfterShutdown(t *testing.T) {
 
 func TestNodeBackendParentContextCancellation(t *testing.T) {
 	ctx, cancelCtx := context.WithCancel(context.Background())
-	nb := newNodeBackend(ctx)
+	nb := newNodeBackend(ctx, eventbus.New())
 
 	cancelCtx()
 
@@ -109,7 +111,7 @@ func TestNodeBackendParentContextCancellation(t *testing.T) {
 }
 
 func TestNodeBackendConcurrentReadyAndShutdown(t *testing.T) {
-	nb := newNodeBackend(t.Context())
+	nb := newNodeBackend(t.Context(), eventbus.New())
 
 	// Calling [nodeBackend.ready] and [nodeBackend.shutdown] concurrently
 	// should not cause issues, and [nodeBackend.Wait] should unblock,