Add SocketUtils for NetworkStack

These utilities can only be used for privileged apps. The underlying
implementation cannot be @SystemApi.

Test: m
Bug: 112869080
Change-Id: Idfa90561102e5b03ab2b79486d3ad46457128bf8
diff --git a/core/java/android/net/TrafficStats.java b/core/java/android/net/TrafficStats.java
index bbf8f97..49c6f74 100644
--- a/core/java/android/net/TrafficStats.java
+++ b/core/java/android/net/TrafficStats.java
@@ -128,10 +128,14 @@
     public static final int TAG_SYSTEM_APP = 0xFFFFFF05;
 
     /** @hide */
+    @SystemApi
+    @TestApi
     public static final int TAG_SYSTEM_DHCP = 0xFFFFFF40;
     /** @hide */
     public static final int TAG_SYSTEM_NTP = 0xFFFFFF41;
     /** @hide */
+    @SystemApi
+    @TestApi
     public static final int TAG_SYSTEM_PROBE = 0xFFFFFF42;
     /** @hide */
     public static final int TAG_SYSTEM_NEIGHBOR = 0xFFFFFF43;
@@ -140,6 +144,8 @@
     /** @hide */
     public static final int TAG_SYSTEM_PAC = 0xFFFFFF45;
     /** @hide */
+    @SystemApi
+    @TestApi
     public static final int TAG_SYSTEM_DHCP_SERVER = 0xFFFFFF46;
 
     private static INetworkStatsService sStatsService;