### 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
DiskUsage most = this.mostAvailableSpaceUsage.get(c.getKey());
                        if (most != null) {
                            most.toShortXContent(builder);
                        }
                    }
                    builder.endObject(); 
                }
                builder.endObject(); 
            }
        }
        builder.endObject(); 
        builder.startObject("shard_sizes");
        {
            for (Map.Entry<String, Long> c : this.shardSizes.entrySet()) {
                builder.humanReadableField(c.getKey() + "_bytes", c.getKey(), new ByteSizeValue(c.getValue()));
            }
        }
        builder.endObject(); 
        builder.startObject("shard_data_set_sizes");
        {
            for (Map.Entry<ShardId, Long> c : this.shardDataSetSizes.entrySet()) {
                builder.humanReadableField(c.getKey() + "_bytes", c.getKey().toString(), new ByteSizeValue(c.getValue()));
            }
        }
        builder.endObject(); 
        builder.startObject("shard_paths");
        {
            for (Map.Entry<ShardRouting, String> c : this.routingToDataPath.entrySet()) {
                builder.field(c.getKey().toString(), c.getValue());
            }