### Description

It should be enough to have ShardId + nodeId key in `routingToDataPath` to find the necessary data path. 
Changing the key would allow us to minimize the size of ClusterInfo size and find the data path when shard changes its status.

`ClusterInfo` might be sent over the wire when cluster allocation explain is executed with `includeDiskInfo=true`.
ShardRouting -> ShardId + nodeId conversion is trivial. The oposit would require additional information that could be faked.

Current key is also used in here:
https://github.com/elastic/elasticsearch/blob/9ebbe1c62bf0157d332f20f392544a1921a710df/server/src/main/java/org/elasticsearch/cluster/ClusterInfo.java#L149-L154
where it produces a string with ShardRouting#shortSummary that is excessive and might be simplified to ShardId + nodeId as well
server/src/test/java/org/elasticsearch/cluster/routing/allocation/decider/DiskThresholdDeciderUnitTests.java
new UnassignedInfo(UnassignedInfo.Reason.INDEX_CREATED, "foo")
        );
        DiscoveryNode node_0 = new DiscoveryNode(
            "node_0",
            buildNewFakeTransportAddress(),
            Collections.emptyMap(),
            new HashSet<>(DiscoveryNodeRole.roles()),
            Version.CURRENT
        );
        DiscoveryNode node_1 = new DiscoveryNode(
            "node_1",
            buildNewFakeTransportAddress(),
            Collections.emptyMap(),
            new HashSet<>(DiscoveryNodeRole.roles()),
            Version.CURRENT
        );
        RoutingTable routingTable = RoutingTable.builder().addAsNew(metadata.index("test")).build();
        ClusterState clusterState = ClusterState.builder(ClusterName.CLUSTER_NAME_SETTING.getDefault(Settings.EMPTY))
            .metadata(metadata)
            .routingTable(routingTable)
            .build();
        clusterState = ClusterState.builder(clusterState).nodes(DiscoveryNodes.builder().add(node_0).add(node_1)).build();
        
        Map<String, DiskUsage> leastAvailableUsages = new HashMap<>();
        leastAvailableUsages.put("node_0", new DiskUsage("node_0", "node_0", "_na_", 100, 0)); 
        leastAvailableUsages.put("node_1", new DiskUsage("node_1", "node_1", "_na_", 100, 0)); 
        Map<String, DiskUsage> mostAvailableUsage = new HashMap<>();
        
        mostAvailableUsage.put("node_0", new DiskUsage("node_0", "node_0", "_na_", 100, randomIntBetween(20, 100)));