[NS01] Create NetworkScore

It's the first patch for refounding network selection. The new
network selection will try to compare the networks by more
factors, and will try to choose the best network after doing
the evaluation of trade-off.
Create the object that will serve to represent network quality
for more comprehensive ranking.

Bug: 143676287
Test: 1. Build pass.
      2. atest FrameworksNetTests

Change-Id: I4b6071d14365aa84d06be9802516fedf527e70f7

tests/net/java/com/android/server/connectivity/LingerMonitorTest.java

@@ -39,6 +39,7 @@ import android.net.NetworkCapabilities;
 import android.net.NetworkFactory;
 import android.net.NetworkInfo;
 import android.net.NetworkMisc;
+import android.net.NetworkScore;
 import android.os.INetworkManagementService;
 import android.text.format.DateUtils;
 
@@ -354,8 +355,10 @@ public class LingerMonitorTest {
         NetworkCapabilities caps = new NetworkCapabilities();
         caps.addCapability(0);
         caps.addTransportType(transport);
+        NetworkScore ns = new NetworkScore();
+        ns.putIntExtension(NetworkScore.LEGACY_SCORE, 50);
         NetworkAgentInfo nai = new NetworkAgentInfo(null, null, new Network(netId), info, null,
-                caps, 50, mCtx, null, mMisc, mConnService, mNetd, mDnsResolver, mNMS,
+                caps, ns, mCtx, null, mMisc, mConnService, mNetd, mDnsResolver, mNMS,
                 NetworkFactory.SerialNumber.NONE);
         nai.everValidated = true;
         return nai;