Fix DV_VALUE replacement bug in config.py (issue #2005)

- Initialize DV_VALUE_NEW and DV_VALUE_OLD from existing DV_VALUE
- Prevents replacement of multi-value DV_VALUE with default [0]
- Fixes error: 'DV_VALUE does not contain enough entries to match DV_KIND or DV_PARAM'

The bug occurred when DV_VALUE_NEW/OLD were missing - they were initialized
to [0] and then overwrote the original DV_VALUE. Now they inherit from
DV_VALUE if it exists, preserving the original values.

Author: aryab08

SU2_PY/SU2/io/config.py

@@ -729,9 +729,9 @@ def read_config(filename):
 
     # hack - twl
     if "DV_VALUE_NEW" not in data_dict:
-        data_dict["DV_VALUE_NEW"] = [0]
+        data_dict["DV_VALUE_NEW"] = data_dict.get("DV_VALUE", [0])
     if "DV_VALUE_OLD" not in data_dict:
-        data_dict["DV_VALUE_OLD"] = [0]
+        data_dict["DV_VALUE_OLD"] = data_dict.get("DV_VALUE", [0])
     if "OPT_ITERATIONS" not in data_dict:
         data_dict["OPT_ITERATIONS"] = 100
     if "OPT_ACCURACY" not in data_dict: