Remove hidden API usage in metrics toString

Remove usage of hidden NetworkType, transport APIs in toString()
implementations of metrics and data usage classes.

The toString implementations can log the transports or network type as
hex or raw indices. While slightly less readable, the metrics classes
and network type APIs are deprecated.

Bug: 174436414
Test: m
Change-Id: I79239a540b66dadd3bbe0a997960530878331358
diff --git a/core/java/android/net/NetworkIdentity.java b/core/java/android/net/NetworkIdentity.java
index 0948a4d..efbfbf9 100644
--- a/core/java/android/net/NetworkIdentity.java
+++ b/core/java/android/net/NetworkIdentity.java
@@ -17,7 +17,6 @@
 package android.net;
 
 import static android.net.ConnectivityManager.TYPE_WIFI;
-import static android.net.ConnectivityManager.getNetworkTypeName;
 import static android.net.ConnectivityManager.isNetworkTypeMobile;
 
 import android.content.Context;
@@ -84,7 +83,7 @@
     @Override
     public String toString() {
         final StringBuilder builder = new StringBuilder("{");
-        builder.append("type=").append(getNetworkTypeName(mType));
+        builder.append("type=").append(mType);
         builder.append(", subType=");
         if (mSubType == SUBTYPE_COMBINED) {
             builder.append("COMBINED");