roachtest: move node-kill operation to pkill/pgrep-based kill approach

For some reason, `StopServiceForVirtualCluster` fails with this error on
drt clusters:

```
20:23:41 node_kill.go:51: operation status: killing node 1  with signal 15
20:23:41 cluster.go:2148: stoping virtual cluster
20:23:41 operation_impl.go:128: operation failure #1: no service for virtual cluster ""
```

The debug message has a bug, the virtual cluster is set to "system" but it
seems like the service discovery process isn't able to determine the cockroach
process based on dns settings in the drt project. This change makes the
node-kill operation more dns-agnostic by looking for the cockroach process.

Epic: none

Release note: None

pkg/cmd/roachtest/operations/BUILD.bazel

@@ -21,7 +21,6 @@ go_library(
         "//pkg/cmd/roachtest/roachtestflags",
         "//pkg/cmd/roachtest/roachtestutil",
         "//pkg/roachprod",
-        "//pkg/roachprod/install",
         "//pkg/util/randutil",
     ],
 )

pkg/cmd/roachtest/operations/node_kill.go

@@ -13,14 +13,14 @@ package operations
 import (
 	"context"
 	"fmt"
+	"strings"
 	"time"
 
 	"github.com/cockroachdb/cockroach/pkg/cmd/roachtest/cluster"
 	"github.com/cockroachdb/cockroach/pkg/cmd/roachtest/operation"
 	"github.com/cockroachdb/cockroach/pkg/cmd/roachtest/option"
 	"github.com/cockroachdb/cockroach/pkg/cmd/roachtest/registry"
 	"github.com/cockroachdb/cockroach/pkg/roachprod"
-	"github.com/cockroachdb/cockroach/pkg/roachprod/install"
 	"github.com/cockroachdb/cockroach/pkg/util/randutil"
 )
 
@@ -79,11 +79,28 @@ func runNodeKill(
 	}
 	o.Status(fmt.Sprintf("killing node %s with signal %d", node.NodeIDsString(), signal))
 
-	stopOpts := option.StopVirtualClusterOpts(install.SystemInterfaceName, node)
-	stopOpts.RoachprodOpts.Sig = signal
-	stopOpts.RoachprodOpts.Wait = true
-	stopOpts.RoachprodOpts.MaxWait = 300 // 5 minutes
-	c.StopServiceForVirtualCluster(ctx, o.L(), stopOpts)
+	err := c.RunE(ctx, option.WithNodes(node), "pkill", fmt.Sprintf("-%d", signal), "-f", "cockroach\\ start")
+	if err != nil {
+		o.Fatal(err)
+	}
+	o.Status(fmt.Sprintf("sent signal %d to node %s, waiting for process to exit", signal, node.NodeIDsString()))
+
+	for {
+		if err := ctx.Err(); err != nil {
+			o.Fatal(err)
+		}
+		err := c.RunE(ctx, option.WithNodes(node), "pgrep", "-f", "cockroach\\ start")
+		if err != nil {
+			if strings.Contains(err.Error(), "status 1") {
+				// pgrep returns error code 1 if no processes are found.
+				break
+			}
+			o.Fatal(err)
+		}
+
+		time.Sleep(1 * time.Second)
+	}
+
 	o.Status(fmt.Sprintf("killed node %s with signal %d", node.NodeIDsString(), signal))
 
 	return &cleanupNodeKill{