add default_column_type to ConvertOptions cdef

Author: vladborovtsov

python/pyarrow/_csv.pyx

@@ -1210,6 +1210,7 @@ cdef class ConvertOptions(_Weakrefable):
     true_values={self.true_values},
     false_values={self.false_values},
     decimal_point={self.decimal_point!r},
+    default_column_type={self.default_column_type},
     strings_can_be_null={self.strings_can_be_null},
     quoted_strings_can_be_null={self.quoted_strings_can_be_null},
     include_columns={self.include_columns},