[BR01.1] Support BpfNetMapsReader

A helper class to *read* java BpfMaps. This is designed to
provide direct bpf access in the caller process through
ConnectivityManager APIs.

The change also removes any statical link to
net-utils-device-common-struct from service-connectivity.
This is because net-utils-device-common-struct is already
included in framework-connectivity. Including it again in
service-connectivity would create a r8 build fail by circular
dependency.

Test: atest FrameworksNetTests:android.net.connectivity.com.android.server.BpfNetMapsTest
Test: atest ConnectivityCoverageTests:android.net.connectivity.com.android.net.module.util.StructTest
Test: atest FrameworksNetTests:android.net.connectivity.android.net.BpfNetMapsReaderTest
Bug: 297836825
Change-Id: I7a6d2eb816d0dc7343167bddd672806b199f44fe
diff --git a/framework/src/android/net/BpfNetMapsUtils.java b/framework/src/android/net/BpfNetMapsUtils.java
index d464e3d..28d5891 100644
--- a/framework/src/android/net/BpfNetMapsUtils.java
+++ b/framework/src/android/net/BpfNetMapsUtils.java
@@ -39,6 +39,8 @@
 import android.os.ServiceSpecificException;
 import android.util.Pair;
 
+import com.android.modules.utils.build.SdkLevel;
+
 import java.util.StringJoiner;
 
 /**
@@ -124,4 +126,15 @@
         }
         return sj.toString();
     }
+
+    public static final boolean PRE_T = !SdkLevel.isAtLeastT();
+
+    /**
+     * Throw UnsupportedOperationException if SdkLevel is before T.
+     */
+    public static void throwIfPreT(final String msg) {
+        if (PRE_T) {
+            throw new UnsupportedOperationException(msg);
+        }
+    }
 }