mmaprototype: make store iteration deterministic

We'll be producing more trace output into datadriven output shortly.
Currently the one test case in TestClusterState that does this
only considers one store, but once we add more test cases we will
run into non-determinism. Avoid this problem.

Author: tbg

pkg/kv/kvserver/allocator/mmaprototype/cluster_state_rebalance_stores.go

@@ -147,7 +147,18 @@ func (re *rebalanceEnv) rebalanceStores(
 	// fdDrain or fdDead, nor do we attempt to shed replicas from a store which
 	// is storeMembershipRemoving (decommissioning). These are currently handled
 	// via replicate_queue.go.
-	for storeID, ss := range re.stores {
+
+	// Need deterministic order for datadriven testing.
+	storeStateSlice := make([]*storeState, 0, len(re.stores))
+	for _, ss := range re.stores {
+		storeStateSlice = append(storeStateSlice, ss)
+	}
+	slices.SortFunc(storeStateSlice, func(a, b *storeState) int {
+		return cmp.Compare(a.StoreID, b.StoreID)
+	})
+
+	for _, ss := range storeStateSlice {
+		storeID := ss.StoreID
 		sls := re.meansMemo.getStoreLoadSummary(ctx, clusterMeans, storeID, ss.loadSeqNum)
 		log.KvDistribution.VEventf(ctx, 2, "evaluating s%d: node load %s, store load %s, worst dim %s",
 			storeID, sls.nls, sls.sls, sls.worstDim)