SystemServer: Support Wifi and WifiScanning for ARC

In ARC, the ArcNetworkService publishes an ARC-version of the
WIFI_SERVICE and WIFI_SCANNING_SERVICE. Don't load the AOSP versions if
it's an ARC device.

This patch eliminates the downstream divergence in SystemServer as part
of trunk-stable efforts. http://ag/24558821 can be reverted after this.

Bug: 301627683
Test: m -j32, betty boots

Change-Id: I11d083266c8c8b1ba87a948b515878f0ede08dd5