### 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/ClusterInfo.java
}
        builder.endObject(); 
        builder.startArray("reserved_sizes");
        {
            for (Map.Entry<NodeAndPath, ReservedSpace> c : this.reservedSpace.entrySet()) {
                builder.startObject();
                {
                    builder.field("node_id", c.getKey().nodeId);
                    builder.field("path", c.getKey().path);
                    c.getValue().toXContent(builder, params);
                }
                builder.endObject(); 
            }
        }
        builder.endArray(); 
        return builder;
    }
    /**
     * Returns a node id to disk usage mapping for the path that has the least available space on the node.
     * Note that this does not take account of reserved space: there may be another path with less available _and unreserved_ space.
     */
    public Map<String, DiskUsage> getNodeLeastAvailableDiskUsages() {
        return this.leastAvailableSpaceUsage;
    }
    /**
     * Returns a node id to disk usage mapping for the path that has the most available space on the node.
     * Note that this does not take account of reserved space: there may be another path with more available _and unreserved_ space.
     */
    public Map<String, DiskUsage> getNodeMostAvailableDiskUsages() {
        return this.mostAvailableSpaceUsage;