Fix regression when deserializing python rows into cython

Fix regression when deserializing python rows into cython

Fixed regression involving pickling of Python rows between the cython and
pure Python implementations of :class:`.Row`, which occurred as part of
refactoring code for version 2.0 with typing. A particular constant were
turned into a string based ``Enum`` for the pure Python version of
:class:`.Row` whereas the cython version continued to use an integer
constant, leading to deserialization failures.

Regression occurred in a4bb502cf95ea3523e4d383c4377e50f402d7d52

Fixes: #9423
Change-Id: Icbd85cacb2d589cef7c246de7064249926146f2e