### 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 ShardId(index, i),
            true,
            PeerRecoverySource.INSTANCE,
            new UnassignedInfo(UnassignedInfo.Reason.INDEX_CREATED, "foo")
        );
        var initialized = ShardRoutingHelper.initialize(unassigned, nodeId, expectedSize);
        var started = ShardRoutingHelper.moveToStarted(initialized, expectedSize);
        return started;
    }
    public long sizeOfUnaccountedShards(RoutingAllocation allocation, RoutingNode node, boolean subtractShardsMovingAway, String dataPath) {
        return DiskThresholdDecider.sizeOfUnaccountedShards(
            node,
            subtractShardsMovingAway,
            dataPath,
            allocation.clusterInfo(),
            allocation.metadata(),
            allocation.routingTable(),
            allocation.unaccountedSearchableSnapshotSize(node)
        );
    }
    public void testSizeShrinkIndex() {
        Map<String, Long> shardSizes = new HashMap<>();
        shardSizes.put("[test][0][p]", 10L);
        shardSizes.put("[test][1][p]", 100L);
        shardSizes.put("[test][2][p]", 500L);
        shardSizes.put("[test][3][p]", 500L);
        ClusterInfo info = new DevNullClusterInfo(Map.of(), Map.of(), shardSizes);
        Metadata.Builder metaBuilder = Metadata.builder();
        metaBuilder.put(
            IndexMetadata.builder("test")