The current UpsertStage/UpdateStage updates documents one by one. It might be nice to introduce a BatchedUpsertStage/BatchedUpdateStage that batches multi-document updates into a single WUOW to fully utilize our batched write functionality and group these related writes together in the oplog. This would be similar to the BatchedDeleteStage and we could utilize the stage here.

We currently call performUpdates where we receive a wholeOp and iterate through each operation. We may potentially want to batch these updates together.