Migrate legacy dhcp server config to DeviceConfig

Legacy dhcp server can also be enabled by resource config.

Bug: 144814607
Test: -build, flash, boot
      -atest TetheringTests

Change-Id: I8ae5fa3d5bbd88129bd0890f71be6f8a1bfec0eb
diff --git a/Tethering/res/values/config.xml b/Tethering/res/values/config.xml
index c29e678..ca290c6 100644
--- a/Tethering/res/values/config.xml
+++ b/Tethering/res/values/config.xml
@@ -49,6 +49,9 @@
         <item>"bt-pan"</item>
     </string-array>
 
+    <!-- Use the old dnsmasq DHCP server for tethering instead of the framework implementation. -->
+    <bool translatable="false" name="config_tether_enable_legacy_dhcp_server">false</bool>
+
     <!-- Dhcp range (min, max) to use for tethering purposes -->
     <string-array translatable="false" name="config_tether_dhcp_range">
     </string-array>
diff --git a/Tethering/res/values/overlayable.xml b/Tethering/res/values/overlayable.xml
index cc7980b..e089d9d 100644
--- a/Tethering/res/values/overlayable.xml
+++ b/Tethering/res/values/overlayable.xml
@@ -21,6 +21,7 @@
             <item type="array" name="config_tether_wifi_p2p_regexs"/>
             <item type="array" name="config_tether_bluetooth_regexs"/>
             <item type="array" name="config_tether_dhcp_range"/>
+            <item type="bool" name="config_tether_enable_legacy_dhcp_server"/>
             <item type="array" name="config_tether_upstream_types"/>
             <item type="bool" name="config_tether_upstream_automatic"/>
             <!-- Configuration values for tethering entitlement check -->