SPM-3918 requires the recipients to propagate their cloning metrics to the coordinator. So the metrics need to be stored in the "mutableState" field (ReshardingRecipientContext/RecipientShardEntry) instead of the "metrics". Additionally, today there is already the "mutableState.bytesCopied" field which is redundant with the "metrics.finalBytesCopiedCount" field. SERVER-98490 will make the recipients still maintain both the metrics in "metrics" and "mutableState" but in 9.1+ we should get rid of the metrics in "metrics".