roachtest: mixedversion test steps are annotated in grafana

Now that we have the ability to create grafana annotations
in roachtests, we can annotate each mixed version step
in grafana.

pkg/cmd/roachtest/roachtestutil/mixedversion/BUILD.bazel

@@ -13,6 +13,7 @@ go_library(
     importpath = "github.com/cockroachdb/cockroach/pkg/cmd/roachtest/roachtestutil/mixedversion",
     visibility = ["//visibility:public"],
     deps = [
+        "//pkg/cmd/roachprod/grafana",
         "//pkg/cmd/roachtest/cluster",
         "//pkg/cmd/roachtest/option",
         "//pkg/cmd/roachtest/roachtestutil",

pkg/cmd/roachtest/roachtestutil/mixedversion/runner.go

@@ -26,6 +26,7 @@ import (
 	"text/tabwriter"
 	"time"
 
+	"github.com/cockroachdb/cockroach/pkg/cmd/roachprod/grafana"
 	"github.com/cockroachdb/cockroach/pkg/cmd/roachtest/cluster"
 	"github.com/cockroachdb/cockroach/pkg/cmd/roachtest/option"
 	"github.com/cockroachdb/cockroach/pkg/cmd/roachtest/roachtestutil/clusterupgrade"
@@ -242,6 +243,13 @@ func (tr *testRunner) runSingleStep(ctx context.Context, ss *singleStep, l *logg
 	defer func() {
 		prefix := fmt.Sprintf("FINISHED [%s]", timeutil.Since(start))
 		tr.logStep(prefix, ss, l)
+		annotation := fmt.Sprintf("(%d): %s", ss.ID, ss.impl.Description())
+		_, err := tr.cluster.AddGrafanaAnnotation(tr.ctx, tr.logger, false /*internal*/, grafana.AddAnnotationRequest{
+			Text: annotation, StartTime: start.UnixMilli(), EndTime: timeutil.Now().UnixMilli(),
+		})
+		if err != nil {
+			l.Printf("Adding Grafana annotation failed: %s", err)
+		}
 	}()
 
 	if err := panicAsError(l, func() error {