Investigate whether BSON depth validation logic can be consolidated

Currently we have two separate implementations to validate the depth of a BSON object: one used by inserts and one used by updates. This can lead to discrepancies like the one described in SERVER-58777. Thus it may be valuable to determine whether it would be possible to consolidate these two implementations into one.

However, this may not be possible due to performance reasons. In particular, the update path uses mutablebson to do the traversal whereas the insert path does not..