### 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/ClusterInfoTests.java
@Override
    protected Writeable.Reader<ClusterInfo> instanceReader() {
        return ClusterInfo::new;
    }
    @Override
    protected ClusterInfo createTestInstance() {
        return new ClusterInfo(
            randomDiskUsage(),
            randomDiskUsage(),
            randomShardSizes(),
            randomDataSetSizes(),
            randomRoutingToDataPath(),
            randomReservedSpace()
        );
    }
    @Override
    protected ClusterInfo mutateInstance(ClusterInfo instance) throws IOException {
        return createTestInstance();
    }
    private static Map<String, DiskUsage> randomDiskUsage() {
        int numEntries = randomIntBetween(0, 128);