Avoid opening log output before start &

Replace tracing logs with task monitor

common/taskmonitor/monitor.go

@@ -0,0 +1,31 @@
+package taskmonitor
+
+import (
+	"time"
+
+	F "github.com/sagernet/sing/common/format"
+	"github.com/sagernet/sing/common/logger"
+)
+
+type Monitor struct {
+	logger  logger.Logger
+	timeout time.Duration
+	timer   *time.Timer
+}
+
+func New(logger logger.Logger, timeout time.Duration) *Monitor {
+	return &Monitor{
+		logger:  logger,
+		timeout: timeout,
+	}
+}
+
+func (m *Monitor) Start(taskName ...any) {
+	m.timer = time.AfterFunc(m.timeout, func() {
+		m.logger.Warn(F.ToString(taskName...), " take too much time to finish!")
+	})
+}
+
+func (m *Monitor) Finish() {
+	m.timer.Stop()
+}