### 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
null,
                null,
                null,
                null,
                new FsInfo(0, null, node3FSInfo),
                null,
                null,
                null,
                null,
                null,
                null,
                null,
                null,
                null
            );
            DiskUsage leastNode = DiskUsage.findLeastAvailablePath(nodeStats);
            DiskUsage mostNode = DiskUsage.findMostAvailable(nodeStats);
            assertDiskUsage(leastNode, node3FSInfo[1]);
            assertDiskUsage(mostNode, node3FSInfo[0]);
        }
    }
    private void assertDiskUsage(DiskUsage usage, FsInfo.Path path) {
        assertNotNull(usage);
        assertNotNull(path);
        assertEquals(usage.toString(), usage.getPath(), path.getPath());
        assertEquals(usage.toString(), usage.getTotalBytes(), path.getTotal().getBytes());
        assertEquals(usage.toString(), usage.getFreeBytes(), path.getAvailable().getBytes());
    }
}