cmd/devp2p, cmd/wnode, whisper: add missing calls to Timer.Stop (#20843)

cmd/devp2p/crawl.go

@@ -63,6 +63,7 @@ func (c *crawler) run(timeout time.Duration) nodeSet {
 		doneCh       = make(chan enode.Iterator, len(c.iters))
 		liveIters    = len(c.iters)
 	)
+	defer timeoutTimer.Stop()
 	for _, it := range c.iters {
 		go c.runIterator(doneCh, it)
 	}

cmd/wnode/main.go

@@ -599,6 +599,7 @@ func messageLoop() {
 	}
 
 	ticker := time.NewTicker(time.Millisecond * 50)
+	defer ticker.Stop()
 
 	for {
 		select {

whisper/whisperv6/whisper.go

@@ -905,6 +905,7 @@ func (whisper *Whisper) update() {
 	defer whisper.wg.Done()
 	// Start a ticker to check for expirations
 	expire := time.NewTicker(expirationCycle)
+	defer expire.Stop()
 
 	// Repeat updates until termination is requested
 	for {