### 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
ShardStats[] stats = new ShardStats[] {
            new ShardStats(test_0, new ShardPath(false, test0Path, test0Path, test_0.shardId()), commonStats0, null, null, null),
            new ShardStats(test_1, new ShardPath(false, test1Path, test1Path, test_1.shardId()), commonStats1, null, null, null),
            new ShardStats(test_1, new ShardPath(false, test1Path, test1Path, test_1.shardId()), commonStats2, null, null, null) };
        Map<String, Long> shardSizes = new HashMap<>();
        Map<ShardId, Long> shardDataSetSizes = new HashMap<>();
        Map<ShardRouting, String> routingToPath = new HashMap<>();
        InternalClusterInfoService.buildShardLevelInfo(
            RoutingTable.EMPTY_ROUTING_TABLE,
            stats,
            shardSizes,
            shardDataSetSizes,
            routingToPath,
            new HashMap<>()
        );
        assertEquals(2, shardSizes.size());
        assertTrue(shardSizes.containsKey(ClusterInfo.shardIdentifierFromRouting(test_0)));
        assertTrue(shardSizes.containsKey(ClusterInfo.shardIdentifierFromRouting(test_1)));
        assertEquals(100L, shardSizes.get(ClusterInfo.shardIdentifierFromRouting(test_0)).longValue());
        assertEquals(1000L, shardSizes.get(ClusterInfo.shardIdentifierFromRouting(test_1)).longValue());
        assertEquals(2, shardDataSetSizes.size());
        assertTrue(shardDataSetSizes.containsKey(test_0.shardId()));
        assertTrue(shardDataSetSizes.containsKey(test_1.shardId()));
        assertEquals(101L, shardDataSetSizes.get(test_0.shardId()).longValue());
        assertEquals(1001L, shardDataSetSizes.get(test_1.shardId()).longValue());
        assertEquals(2, routingToPath.size());
        assertTrue(routingToPath.containsKey(test_0));
        assertTrue(routingToPath.containsKey(test_1));
        assertEquals(test0Path.getParent().getParent().getParent().toAbsolutePath().toString(), routingToPath.get(test_0));
        assertEquals(test1Path.getParent().getParent().getParent().toAbsolutePath().toString(), routingToPath.get(test_1));