### 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/DiskUsageTests.java
0,
                null,
                null,
                null,
                null,
                null,
                new FsInfo(0, null, nodeFSInfo),
                null,
                null,
                null,
                null,
                null,
                null,
                null,
                null,
                null
            );
            DiskUsage leastNode = DiskUsage.findLeastAvailablePath(nodeStats);
            DiskUsage mostNode = DiskUsage.findMostAvailable(nodeStats);
            assertNull("node_2 should have been skipped", leastNode);
            assertNull("node_2 should have been skipped", mostNode);
        }
        {
            FsInfo.Path[] node3FSInfo = new FsInfo.Path[] {
                new FsInfo.Path("/most", "/dev/sda", 100, 90, 70),
                new FsInfo.Path("/least", "/dev/sda", 10, -1, 0), };
            NodeStats nodeStats = new NodeStats(
                new DiscoveryNode("node_3", buildNewFakeTransportAddress(), emptyMap(), emptySet(), Version.CURRENT),
                0,
                null,