### 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/main/java/org/elasticsearch/cluster/routing/allocation/decider/DiskThresholdDecider.java
String dataPath,
        ClusterInfo clusterInfo,
        Metadata metadata,
        RoutingTable routingTable,
        long sizeOfUnaccountableSearchableSnapshotShards
    ) {
        
        final ClusterInfo.ReservedSpace reservedSpace = clusterInfo.getReservedSpace(node.nodeId(), dataPath);
        long totalSize = reservedSpace.getTotal();
        
        
        
        for (ShardRouting routing : node.initializing()) {
            if (routing.relocatingNodeId() == null && metadata.getIndexSafe(routing.index()).isSearchableSnapshot() == false) {
                
                
                
                
                continue;
            }
            if (reservedSpace.containsShardId(routing.shardId())) {
                continue;
            }
            final String actualPath = clusterInfo.getDataPath(routing);
            
            
            if (actualPath == null || actualPath.equals(dataPath)) {
                totalSize += getExpectedShardSize(
                    routing,
                    Math.max(routing.getExpectedShardSize(), 0L),