roachtest: prefix all logs with worker tags

Previously, many of the runner logs didn't have the worker tags.
This was inadequate because we couldn't break up the logs by wX
tags to see what each worker is doing.
This PR prefixes the worker tags to logs that were missing them.

Epic: none
Fixes: cockroachdb#114045
Release note: None

pkg/cmd/roachtest/cluster.go

@@ -1927,7 +1927,7 @@ func (c *clusterImpl) Get(
 	return errors.Wrap(roachprod.Get(ctx, l, c.MakeNodes(opts...), src, dest), "cluster.Get")
 }
 
-// Put a string into the specified file on the remote(s).
+// PutString into the specified file on the remote(s).
 func (c *clusterImpl) PutString(
 	ctx context.Context, content, dest string, mode os.FileMode, nodes ...option.Option,
 ) error {

pkg/cmd/roachtest/test_runner.go

@@ -363,8 +363,17 @@ func (r *testRunner) Run(
 		if err := r.stopper.RunAsyncTask(ctx, "worker", func(ctx context.Context) {
 			defer wg.Done()
 
+			name := fmt.Sprintf("w%d", i)
+			formattedPrefix := fmt.Sprintf("[%s] ", name)
+			childLogger, e := l.ChildLogger(name, logger.LogPrefix(formattedPrefix))
+			if e != nil {
+				l.Printf("unable to create logger %s: %s", name, e)
+				return
+			}
+			l = childLogger
+
 			err := r.runWorker(
-				ctx, fmt.Sprintf("w%d", i) /* name */, r.work, qp,
+				ctx, name, r.work, qp,
 				r.stopper.ShouldQuiesce(),
 				clusterFactory,
 				clustersOpt,