Add Thread resource overlay support

This CL adds resource overlay support to allow developers to
change the default configuration of using the location country code.

Bug: b/311324956
Test: Set the resource overlay in cuttlefish, check the default
      configuration via the command `dumpsys thread_network`.

Change-Id: Ide853975e8244f06a382b2eda4844e030539b95d
diff --git a/service/ServiceConnectivityResources/res/values/overlayable.xml b/service/ServiceConnectivityResources/res/values/overlayable.xml
index 4c85e8c..1c07599 100644
--- a/service/ServiceConnectivityResources/res/values/overlayable.xml
+++ b/service/ServiceConnectivityResources/res/values/overlayable.xml
@@ -43,6 +43,9 @@
             <item type="string" name="config_ethernet_iface_regex"/>
             <item type="integer" name="config_validationFailureAfterRoamIgnoreTimeMillis" />
             <item type="integer" name="config_netstats_validate_import" />
+
+            <!-- Configuration values for ThreadNetworkService -->
+            <item type="bool" name="config_thread_location_use_for_country_code_enabled" />
         </policy>
     </overlayable>
 </resources>