This ticket will require modifying the FLE2EncryptionPlaceholder type type to support placeholders with range indexes, and then make sure that the placeholder is properly serialized to BSON.

The value of a range encryption placeholder should be a BSONArray with two entries, one representing the lower bound, and one representing the upper bound. This should be verified at parse-time if the encryption type is range.

Will need to communicate downstream to Server Security to make sure that the BSON format is known for actual encryption by libmongocrypt.