all: consistently initialize Logf when creating tsdial.Dialers

Most visible when using tsnet.Server, but could have resulted in dropped
messages in a few other places too.

Fixes #5743

Signed-off-by: Mihai Parparita <mihai@tailscale.com>

cmd/tsconnect/wasm/wasm_js.go

@@ -96,7 +96,7 @@ func newIPN(jsConfig js.Value) map[string]any {
 	logtail := logtail.NewLogger(c, log.Printf)
 	logf := logtail.Logf
 
-	dialer := new(tsdial.Dialer)
+	dialer := &tsdial.Dialer{Logf: logf}
 	eng, err := wgengine.NewUserspaceEngine(logf, wgengine.Config{
 		Dialer: dialer,
 	})