### 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
private long total;
            private HashSet<ShardId> shardIds = new HashSet<>();
            public ReservedSpace build() {
                assert shardIds != null : "already built";
                final ReservedSpace reservedSpace = new ReservedSpace(total, shardIds);
                shardIds = null;
                return reservedSpace;
            }
            public Builder add(ShardId shardId, long reservedBytes) {
                assert shardIds != null : "already built";
                assert reservedBytes >= 0 : reservedBytes;
                shardIds.add(shardId);
                total += reservedBytes;
                return this;
            }
        }
    }
}