Allow scan hidden networks during scan-only mode

In current implementation, hidden networks were not scanned
during scan only mode.
This commit add an option to include them in the scan, with default
similar to existing behavior.

Bug: 143588535
Test: atest com.android.wifi.server
Change-Id: I9bb4ecbe232f222b331f3c031cd803109beb7860
diff --git a/service/res/values/config.xml b/service/res/values/config.xml
index eb9928b..e35fcf0 100644
--- a/service/res/values/config.xml
+++ b/service/res/values/config.xml
@@ -220,4 +220,7 @@
         <item>80</item>
         <item>160</item>
     </integer-array>
+
+    <!-- Indicates that hidden networks are to be scanned during scan only mode -->
+    <bool translatable="false" name="config_wifiScanHiddenNetworksScanOnlyMode">false</bool>
 </resources>