copy: enhance copyfrom roachtest

Add 3 node config for more retry coverage and turn off backups since its
a perf test.

Release note: none
Epic: CRDB-25321
Informs: cockroachdb#99327

pkg/cmd/roachtest/tests/copyfrom.go

@@ -113,7 +113,7 @@ func runCopyFromPG(ctx context.Context, t test.Test, c cluster.Cluster, sf int)
 
 func runCopyFromCRDB(ctx context.Context, t test.Test, c cluster.Cluster, sf int, atomic bool) {
 	c.Put(ctx, t.Cockroach(), "./cockroach", c.All())
-	c.Start(ctx, t.L(), option.DefaultStartOpts(), install.MakeClusterSettings(), c.All())
+	c.Start(ctx, t.L(), option.DefaultStartOptsNoBackups(), install.MakeClusterSettings(), c.All())
 	initTest(ctx, t, c, sf)
 	db, err := c.ConnE(ctx, t.L(), 1)
 	require.NoError(t, err)
@@ -151,6 +151,7 @@ func registerCopyFrom(r registry.Registry) {
 		nodes int
 	}{
 		{sf: 1, nodes: 1},
+		{sf: 1, nodes: 3},
 	}
 
 	for _, tc := range testcases {