Make Row type comparable

This PR addresses #1957 to make ``row`` type comparable and implements the ``EQUAL`` and ``NOT_EQUAL`` operators for the ``row`` type.
This doesn't quite work, because the stack type of row is json containing the stack encodings of its field types, and the field types may have equality defined in a way that is not the same as comparing their bytes directly. Instead you need to unpack the fields and compare them using the appropriate field type .equalTo method