SERVER-77958 added the 'keyCharacteristics' and 'readWriteDistribution' options to the analyzeShardKey command. The analyzeShardKey command currently returns the metrics about the read and write distribution under the 'readDistribution' and 'writeDistribution' fields, respectively. However, it returns the metrics about the characteristics of the shard key at the outer-most level. These metrics should go under new field named 'keyCharacteristics' field for clarity.