roachtest: add a multi-store lease rebalancing roachtest

We rencetly added a multi-store roachtest for rebalancing, and this
one is for moving leases.

Fixes cockroachdb#79841

Release note: None

pkg/cmd/roachtest/tests/rebalance_load.go

@@ -178,6 +178,36 @@ func registerRebalanceLoad(r registry.Registry) {
 			},
 		},
 	)
+	r.Add(
+		registry.TestSpec{
+			Name:    `rebalance/by-load/leases/ssds=2`,
+			Owner:   registry.OwnerKV,
+			Cluster: r.MakeClusterSpec(4, spec.SSD(2)), // the last node is just used to generate load
+			Run: func(ctx context.Context, t test.Test, c cluster.Cluster) {
+				if c.IsLocal() {
+					t.Fatal("cannot run multi-store in local mode")
+				}
+
+				// Increase replication to 6 in order to allow lease shedding get the
+				// cluster perfectly balanced. Note that we have 6 stores here on 3
+				// nodes, and we disable replica moves. If we only have 3 replicas we
+				// may have hot stores that can only shed leases to other hot stores,
+				// and therefore we may never get to a balanced lease count.
+				db := c.Conn(ctx, t.L(), 1)
+				defer db.Close()
+				exec := func(stmt string) {
+					_, err := db.ExecContext(ctx, stmt)
+					require.NoError(t, err)
+				}
+				exec("ALTER RANGE default CONFIGURE ZONE USING num_replicas=6")
+				exec("ALTER DATABASE system CONFIGURE ZONE USING num_replicas=6")
+
+				rebalanceLoadRun(
+					ctx, t, c, "leases", 6*time.Minute, concurrency, false, /* mixedVersion */
+				)
+			},
+		},
+	)
 	r.Add(
 		registry.TestSpec{
 			Name:    `rebalance/by-load/replicas`,