Remove use of ImmutableOpenIntMap in IndexRoutingTable (#86368)

The routing table builder uses an hppc based immutable map to keep track
of shard id to shard table. However, when building the final routing
table, it is just converted to an array. This commit switches to a
HashMap.

relates #86239

server/src/main/java/org/elasticsearch/cluster/routing/IndexRoutingTable.java

@@ -18,7 +18,6 @@
 import org.elasticsearch.cluster.routing.RecoverySource.PeerRecoverySource;
 import org.elasticsearch.cluster.routing.RecoverySource.SnapshotRecoverySource;
 import org.elasticsearch.common.Randomness;
-import org.elasticsearch.common.collect.ImmutableOpenIntMap;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.util.CollectionUtils;
@@ -29,6 +28,7 @@
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
@@ -66,7 +66,7 @@ public class IndexRoutingTable implements SimpleDiffable<IndexRoutingTable> {
 
     private final List<ShardRouting> allActiveShards;
 
-    IndexRoutingTable(Index index, ImmutableOpenIntMap<IndexShardRoutingTable> shards) {
+    IndexRoutingTable(Index index, Map<Integer, IndexShardRoutingTable> shards) {
         this.index = index;
         this.shuffler = new RotationShardShuffler(Randomness.get().nextInt());
         this.shards = new IndexShardRoutingTable[shards.size()];
@@ -328,7 +328,7 @@ public static Builder builder(Index index) {
     public static class Builder {
 
         private final Index index;
-        private final ImmutableOpenIntMap.Builder<IndexShardRoutingTable> shards = ImmutableOpenIntMap.builder();
+        private final Map<Integer, IndexShardRoutingTable> shards = new HashMap<>();
 
         public Builder(Index index) {
             this.index = index;
@@ -487,7 +487,7 @@ private Builder initializeEmpty(IndexMetadata indexMetadata, UnassignedInfo unas
         }
 
         public Builder addReplica() {
-            for (var shardNumber : shards.keys()) {
+            for (var shardNumber : shards.keySet()) {
                 ShardId shardId = new ShardId(index, shardNumber);
                 // version 0, will get updated when reroute will happen
                 ShardRouting shard = ShardRouting.newUnassigned(
@@ -502,7 +502,7 @@ public Builder addReplica() {
         }
 
         public Builder removeReplica() {
-            for (var shardId : shards.keys()) {
+            for (var shardId : shards.keySet()) {
                 IndexShardRoutingTable indexShard = shards.get(shardId);
                 if (indexShard.replicaShards().isEmpty()) {
                     // nothing to do here!
@@ -557,7 +557,7 @@ public Builder addShard(ShardRouting shard) {
         }
 
         public IndexRoutingTable build() {
-            return new IndexRoutingTable(index, shards.build());
+            return new IndexRoutingTable(index, shards);
         }
     }