We compute the size used in DocumentStorage here and then again here.

The second time, we call getApproximateSize() on the geoNearPoint and searchHighlight metadata fields.

We should change getApproximateSize() to still count the approximate size of geoNearPoint and searchHighlight, but not to double count the space metadata fields use in DocumentStorage.

As part of this work, we may be able to revert the "allowDiskUse: true" added in this line as part of SERVER-40555.